MicroRNA 21 (miR-21) and miR-181b couple with NFI-A to generate myeloid-derived suppressor cells and promote immunosuppression in late sepsis

Understanding the immunosuppressive microenvironment of glioma: mechanistic insights and clinical perspectives

Glioblastoma (GBM), the predominant and primary malignant intracranial tumor, poses a formidable challenge due to its immunosuppressive microenvironment, thereby confounding conventional therapeutic interventions. Despite the established treatment regimen comprising surgical intervention, radiotherapy, temozolomide administration, and the exploration of emerging modalities such as immunotherapy and integration of medicine and engineering technology therapy, the efficacy of these approaches remains constrained, resulting in suboptimal prognostic outcomes. In recent years, intensive scrutiny of the inhibitory and immunosuppressive milieu within GBM has underscored the significance of cellular constituents of the GBM microenvironment and their interactions with malignant cells and neurons. Novel immune and targeted therapy strategies have emerged, offering promising avenues for advancing GBM treatment. One pivotal mechanism orchestrating immunosuppression in GBM involves the aggregation of myeloid-derived suppressor cells (MDSCs), glioma-associated macrophage/microglia (GAM), and regulatory T cells (Tregs). Among these, MDSCs, though constituting a minority (4-8%) of CD45+ cells in GBM, play a central component in fostering immune evasion and propelling tumor progression, angiogenesis, invasion, and metastasis. MDSCs deploy intricate immunosuppressive mechanisms that adapt to the dynamic tumor microenvironment (TME). Understanding the interplay between GBM and MDSCs provides a compelling basis for therapeutic interventions. This review seeks to elucidate the immune regulatory mechanisms inherent in the GBM microenvironment, explore existing therapeutic targets, and consolidate recent insights into MDSC induction and their contribution to GBM immunosuppression. Additionally, the review comprehensively surveys ongoing clinical trials and potential treatment strategies, envisioning a future where targeting MDSCs could reshape the immune landscape of GBM. Through the synergistic integration of immunotherapy with other therapeutic modalities, this approach can establish a multidisciplinary, multi-target paradigm, ultimately improving the prognosis and quality of life in patients with GBM.

Critical role of miR-21/exosomal miR-21 in autophagy pathway

Activation of autophagy, a process of cellular stress response, leads to the breakdown of proteins, organelles, and other parts of the cell in lysosomes, and can be linked to several ailments, such as cancer, neurological diseases, and rare hereditary syndromes. Thus, its regulation is very carefully monitored. Transcriptional and post-translational mechanisms domestically or in whole organisms utilized to control the autophagic activity, have been heavily researched. In modern times, microRNAs (miRNAs) are being considered to have a part in post-translational orchestration of the autophagic activity, with miR-21 as one of the best studied miRNAs, it is often more than expressed in cancer cells. This regulatory RNA is thought to play a major role in a plethora of processes and illnesses including growth, cancer, cardiovascular disease, and inflammation. Different studies have suggested that a few autophagy-oriented genes, such as PTEN, Rab11a, Atg12, SIPA1L2, and ATG5, are all targeted by miR-21, indicating its essential role in the regulation.

Immunomodulatory actions of myeloid-derived suppressor cells in the context of innate immunity

Myeloid-derived suppressor cells (MDSCs) are notable innate immune cells, which are further divided into two subpopulations, i.e., monocytic and granulocytic. These cells are traditionally considered to mainly suppress the T-cell responses. However, more updated data indicate that their properties are rather immunomodulatory than solely immunosuppressive. Indeed, MDSCs display extensive crosstalk with other either innate or adaptive immune cells, and, according to the situation under which they are triggered, they may enhance or attenuate the immune response. However, their positive role in host's defense mechanisms under specific conditions is rarely discussed in the literature. In this mini-review, the authors briefly summarise the mechanisms of action of MDSCs under distinct conditions, such as infections and malignancies, with a particular emphasis on their role as components of the innate immunity system.

Inhibitory effect of microRNA-21 on pathways and mechanisms involved in cardiac fibrosis development

Cardiac fibrosis is a pivotal cardiovascular disease (CVD) process and represents a notable health concern worldwide. While the complex mechanisms underlying CVD have been widely investigated, recent research has highlighted microRNA-21's (miR-21) role in cardiac fibrosis pathogenesis. In this narrative review, we explore the molecular interactions, focusing on the role of miR-21 in contributing to cardiac fibrosis. Various signaling pathways, such as the RAAS, TGF-β, IL-6, IL-1, ERK, PI3K-Akt, and PTEN pathways, besides dysregulation in fibroblast activity, matrix metalloproteinases (MMPs), and tissue inhibitors of MMPs cause cardiac fibrosis. Besides, miR-21 in growth factor secretion, apoptosis, and endothelial-to-mesenchymal transition play crucial roles. miR-21 capacity regulatory function presents promising insights for cardiac fibrosis. Moreover, this review discusses numerous approaches to control miR-21 expression, including antisense oligonucleotides, anti-miR-21 compounds, and Notch signaling modulation, all novel methods of cardiac fibrosis inhibition. In summary, this narrative review aims to assess the molecular mechanisms of cardiac fibrosis and its essential miR-21 function.

DLK1 overexpression improves sepsis-induced cardiac dysfunction and fibrosis in mice through the TGF-β1/Smad3 signaling pathway and MMPs

Sepsis is a serious inflammatory disease caused by bacterial infection. Cardiovascular dysfunction and remodeling are serious complications of sepsis, which can significantly affect sepsis patients' mortality. Delta-like homologue 1 (DLK1) has been reported could inhibit cardiac myofibroblast differentiation. However, the function of DLK1 in sepsis is unknown. In the present study, the DLK1 expression was first identified based on the online dataset GSE79962 analysis and cecal ligation and puncture (CLP)-induced sepsis mouse model. DLK1 expression was significantly reduced in septic heart tissues. In septic mouse heart, CLP operation decreased the fractional shortening (EF) (%) and ejection fraction (FS) (%) and caused significant edema, disordered myofilament arrangement, and degradation and necrosis in myocardial cells; CLP operation also increased collagen deposition and elevated the protein levels of fibrotic markers (α-SMA and F-actin). DLK1 overexpression in septic mice could effectively increase EF (%) and FS (%), attenuate CLP-caused ECM degradation and deposition and partially inhibit the CLP-induced TGF-β1/Smad signaling activation. In conclusion, DLK1 expression was poorly expressed in the CLP-induced septic mouse heart. DLK1 overexpression partially alleviated sepsis-induced cardiac dysfunction and fibrosis, with the involvement of the TGF-β1/Smad3 signaling pathway and MMPs.

S100A8/A9: An emerging player in sepsis and sepsis-induced organ injury

Sepsis, the foremost contributor to mortality in intensive care unit patients, arises from an uncontrolled systemic response to invading infections, resulting in extensive harm across multiple organs and systems. Recently, S100A8/A9 has emerged as a promising biomarker for sepsis and sepsis-induced organ injury, and targeting S100A8/A9 appeared to ameliorate inflammation-induced tissue damage and improve adverse outcomes. S100A8/A9, a calcium-binding heterodimer mainly found in neutrophils and monocytes, serves as a causative molecule with pro-inflammatory and immunosuppressive properties, which are vital in the pathogenesis of sepsis. Therefore, improving our comprehension of how S100A8/A9 acts as a pathological player in the development of sepsis is imperative for advancing research on sepsis. Our review is the first-to the best of our knowledge-to discuss the biology of S100A8/A9 and its release mechanisms, summarize recent advances concerning the vital roles of S100A8/A9 in sepsis and the consequential organ damage, and underscore its potential as a promising diagnostic biomarker and therapeutic target for sepsis.

miRNAs as key modulators between normal cells and tumor microenvironment interactions

The tumor microenvironment (TME) is well-defined target for understanding tumor progression and various cell types. Major elements of the tumor microenvironment are the followings: endothelial cells, fibroblasts, signaling molecules, extracellular matrix, and infiltrating immune cells. MicroRNAs (miRNAs) are a group of small noncoding RNAs with major functions in the gene expression regulation at post-transcriptional level that have also appeared to exerts key functions in the cancer initiation/progression in diverse biological processes and the tumor microenvironment. This study summarized various roles of miRNAs in the complex interactions between the tumor and normal cells in their microenvironment.

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.

Role of miRNA dysregulation in sepsis

Background

Sepsis is defined as a state of multisystem organ dysfunction secondary to a dysregulated host response to infection and causes millions of deaths worldwide annually. Novel ways to counteract this disease are needed and such tools may be heralded by a detailed understanding of its molecular pathogenesis. MiRNAs are small RNA molecules that target mRNAs to inhibit or degrade their translation and have important roles in several disease processes including sepsis.

Main body

The current review adopted a strategic approach to analyzing the widespread literature on the topic of miRNAs and sepsis. A pubmed search of “miRNA or microRNA or small RNA and sepsis not review” up to and including January 2021 led to 1140 manuscripts which were reviewed. Two hundred and thirty-three relevant papers were scrutinized for their content and important themes on the topic were identified and subsequently discussed, including an in-depth look at deregulated miRNAs in sepsis in peripheral blood, myeloid derived suppressor cells and extracellular vesicles.

Conclusion

Our analysis yielded important observations. Certain miRNAs, namely miR-150 and miR-146a, have consistent directional changes in peripheral blood of septic patients across numerous studies with strong data supporting a role in sepsis pathogenesis. Furthermore, a large body of literature show miRNA signatures of clinical relevance, and lastly, many miRNAs deregulated in sepsis are associated with the process of endothelial dysfunction. This review offers a widespread, up-to-date and detailed discussion of the role of miRNAs in sepsis and is meant to stimulate further work in the field due to the potential of these small miRNAs in prompt diagnostics, prognostication and therapeutic agency.

Supplementary Information

The online version contains supplementary material available at 10.1186/s10020-022-00527-z.

Myeloid derived suppressor cells in tumor microenvironment: Interaction with innate lymphoid cells

Human myeloid-derived suppressor cells (MDSC) represent a stage of immature myeloid cells and two main subsets can be identified: monocytic and polymorphonuclear. MDSC contribute to the establishment of an immunosuppressive tumor microenvironment (TME). The presence and the activity of MDSC in patients with different tumors correlate with poor prognosis. As previously reported, MDSC promote tumor growth and use different mechanisms to suppress the immune cell-mediated anti-tumor activity. Immunosuppression mechanisms used by MDSC are broad and depend on their differentiation stage and on the pathological context. It is known that some effector cells of the immune system can play an important role in the control of tumor progression and metastatic spread. In particular, innate lymphoid cells (ILC) contribute to control tumor growth representing a potential, versatile and, immunotherapeutic tool. Despite promising results obtained by using new cellular immunotherapeutic approaches, a relevant proportion of patients do not benefit from these therapies. Novel strategies have been investigated to overcome the detrimental effect exerted by the immunosuppressive component of TME (i.e. MDSC). In this review, we summarized the characteristics and the interactions occurring between MDSC and ILC in different tumors discussing how a deeper knowledge on MDSC biology could represent an important target for tumor immunotherapy capable of decreasing immunosuppression and enhancing anti-tumor activity exerted by immune cells.

Expression of MicroRNAs in Sepsis-Related Organ Dysfunction: A Systematic Review

Sepsis is a critical condition characterized by increased levels of pro-inflammatory cytokines and proliferating cells such as neutrophils and macrophages in response to microbial pathogens. Such processes lead to an abnormal inflammatory response and multi-organ failure. MicroRNAs (miRNA) are single-stranded non-coding RNAs with the function of gene regulation. This means that miRNAs are involved in multiple intracellular pathways and thus contribute to or inhibit inflammation. As a result, their variable expression in different tissues and organs may play a key role in regulating the pathophysiological events of sepsis. Thanks to this property, miRNAs may serve as potential diagnostic and prognostic biomarkers in such life-threatening events. In this narrative review, we collect the results of recent studies on the expression of miRNAs in heart, blood, lung, liver, brain, and kidney during sepsis and the molecular processes in which they are involved. In reviewing the literature, we find at least 122 miRNAs and signaling pathways involved in sepsis-related organ dysfunction. This may help clinicians to detect, prevent, and treat sepsis-related organ failures early, although further studies are needed to deepen the knowledge of their potential contribution.

Regulatory effects of miRNA-126 on Th cell differentiation and cytokine expression in allergic rhinitis

BACKGROUND

Allergic rhinitis (AR) is a common disease worldwide. Imbalances in T helper (Th) cell differentiation and the dysregulation of related cytokines form the immunological basis of AR. miR-126 may play an important regulatory role in AR as a new marker and predictor of the disease. Therefore, the aim of this study was to explore the regulatory effects of miR-126 on Th cell differentiation and cytokine expression in AR.

METHODS

T lymphocytes and rat models were transfected with a miR-126 mimic and an inhibitor. The expression of miR-126 and Th cell-related cytokines was detected by RT-qPCR and western blotting. The serum IgE levels were detected using ELISA. In the nasal mucosa, pathological changes were observed by HE staining, protein expression was detected by immunohistochemistry, and the differentiation ratio of Th cell subsets was detected by flow cytometry.

RESULTS

During the occurrence and development of AR, the expression of miR-126 and the IgE levels were increased in the AR group. The number of Treg cell subsets decreased in the AR rats, increased after the miR-126 agomir intervention and decreased after miR-126 antagomir intervention. The number of Th1 and Th2 cell subsets increased in the AR rats, decreased after miR-126 agomir intervention and increased after the miR-126 antagomir intervention.

CONCLUSION

We propose that miR-126 may be involved in the pathogenesis of AR by positively regulating the expression of Treg cytokines and negatively regulating the expression of the Th1 and Th2 cytokines.

Modes of action and diagnostic value of miRNAs in sepsis

Sepsis is a clinical syndrome defined as a dysregulated host response to infection resulting in life-threatening organ dysfunction. Sepsis is a major public health concern associated with one in five deaths worldwide. Sepsis is characterized by unbalanced inflammation and profound and sustained immunosuppression, increasing patient susceptibility to secondary infections and mortality. microRNAs (miRNAs) play a central role in the control of many biological processes, and deregulation of their expression has been linked to the development of oncological, cardiovascular, neurodegenerative and metabolic diseases. In this review, we discuss the role of miRNAs in sepsis pathophysiology. Overall, miRNAs are seen as promising biomarkers, and it has been proposed to develop miRNA-based therapies for sepsis. Yet, the picture is not so straightforward because of the versatile and dynamic features of miRNAs. Clearly, more research is needed to clarify the expression and role of miRNAs in sepsis, and to promote the use of miRNAs for sepsis management.

Stochastic Collision Electrochemistry from Single Pt Nanoparticles: Electrocatalytic Amplification and MicroRNA Sensing

Single-particle collisions have made many achievements in basic research, but challenges still exist due to their low collision frequency and selectivity in complex samples. In this work, we developed an "on-off-on" strategy based on Pt nanoparticles (PtNPs) that catalyze N₂H₄ collision signals on the surface of carbon ultramicroelectrodes and established a new method for the detection of miRNA21 with high selectivity and sensitivity. PtNPs catalyze the reduction of N₂H₄ on the surface of carbon ultramicroelectrodes to generate a stepped collision signal, which is in the "on" state. The single-stranded DNA paired with miRNA21 is coupled with PtNPs to form the complex DNA/PtNPs. Because PtNPs are covered by DNA, the electrocatalytic collision of N₂H₄ oxidation is inhibited. At this time, the signal is in the "off" state. When miRNA21 is added, the strong complementary pairing between miRNA21 and DNA destroys the electrostatic adsorption of DNA/PtNP conjugates and restores the electrocatalytic performance of PtNPs, and the signal is in the "on" state again. Based on this, a new method for detecting miRNA21 was established. It provides a new way for small-molecule sensing and has a wide range of applications in electroanalysis, electrocatalysis, and biosensing.

Thymoquinone modulates the expression of sepsis‑related microRNAs in a CLP model

Sepsis is a clinical syndrome common in critical care settings. In the present study, the therapeutic effect of thymoquinone (TQ) on the expression of sepsis-related microRNAs (miRNAs/miRs), levels of inflammatory markers, organ dysfunction and mortality were investigated in a cecal ligation and puncture (CLP) rat model. A single dose of TQ (1 mg/kg) was administered to animals 24 h after CLP and the mortality rate was assessed up to 7 days following the induction of sepsis. In addition, blood samples were collected at different time points and the expression levels of miRNAs (i.e. miR-16, miR-21, miR-27a and miR-34a) were examined, along with the levels of inflammatory cytokines (i.e. TNF-α, IL-1α, IL-2, IL-6 and IL-10) and sepsis markers (i.e. C-reactive protein, endothelial cell-specific molecule-1, VEGF, procalcitonin and D-dimer). Liver, kidney and lung tissues were also collected for further histological examination. Treatment with TQ significantly downregulated the miRNA expression levels, as well as the levels of inflammatory cytokines and early-stage sepsis biomarkers by 30-70% at 12-36 h (P<0.05). Furthermore, CLP model rats treated with TQ exhibited an ~80% increase in survival rate compared with that in the untreated CLP group. In addition, TQ induced the preservation of organ function and structure. In conclusion, the present study demonstrated a promising therapeutic effect of TQ against the sequelae of sepsis.

MicroRNA-21 Is a Versatile Regulator and Potential Treatment Target in Central Nervous System Disorders

MicroRNAs (miRNAs) are a class of endogenous, non-coding, single-stranded RNAs with a length of approximately 22 nucleotides that are found in eukaryotes. miRNAs are involved in the regulation of cell differentiation, proliferation, invasion, apoptosis, and metabolism by regulating the expression of their target genes. Emerging studies have suggested that various miRNAs play key roles in the pathogenesis of central nervous system (CNS) disorders and may be viable therapeutic targets. In particular, miR-21 has prominently emerged as a focus of increasing research on the mechanisms of its involvement in CNS disorders. Herein, we reviewed recent studies on the critical roles of miR-21, including its dysregulated expression and target genes, in the regulation of pathophysiological processes of CNS disorders, with a special focus on apoptosis and inflammation. Collectively, miR-21 is a versatile regulator in the progression of CNS disorders and could be a promising biomarker and therapeutic target for these diseases. An in-depth understanding of the mechanisms by which miR-21 affects the pathogenesis of CNS disorders could pave the way for miR-21 to serve as a therapeutic target for these conditions.

Regulatory Role of Non-Coding RNAs on Immune Responses During Sepsis

Sepsis is resulted from a systemic inflammatory response to bacterial, viral, or fungal agents. The induced inflammatory response by these microorganisms can lead to multiple organ system failure with devastating consequences. Recent studies have shown altered expressions of several non-coding RNAs such as long non-coding RNAs (lncRNAs), microRNAs (miRNAs) and circular RNAs (circRNAs) during sepsis. These transcripts have also been found to participate in the pathogenesis of multiple organ system failure through different mechanisms. NEAT1, MALAT1, THRIL, XIST, MIAT and TUG1 are among lncRNAs that participate in the pathoetiology of sepsis-related complications. miR-21, miR-155, miR-15a-5p, miR-494-3p, miR-218, miR-122, miR-208a-5p, miR-328 and miR-218 are examples of miRNAs participating in these complications. Finally, tens of circRNAs such as circC3P1, hsa_circRNA_104484, hsa_circRNA_104670 and circVMA21 and circ-PRKCI have been found to affect pathogenesis of sepsis. In the current review, we describe the role of these three classes of noncoding RNAs in the pathoetiology of sepsis-related complications.

Myeloid-Derived Suppressor Cells (MDSCs) and the Immunoinflammatory Response to Injury (Mini Review)

ABSTRACT

Myeloid-derived suppressor cells (MDSCs) are a heterogenous population of immature myeloid cells hallmarked by their potent immunosuppressive function in a vast array of pathologic conditions. MDSCs have recently been shown to exhibit marked expansion in acute inflammatory states including traumatic injury, burn, and sepsis. Although MDSCs have been well characterized in cancer, there are significant gaps in our knowledge of their functionality in trauma and sepsis, and their clinical significance remains unclear. It is suggested that MDSCs serve an important role in quelling profound inflammatory responses in the acute setting; however, MDSC accumulation may also predispose patients to developing persistent immune dysregulation with increased risk for nosocomial infections, sepsis, and multiorgan failure. Whether MDSCs may serve as the target for novel therapeutics or an important biomarker in trauma and sepsis is yet to be determined. In this review, we will discuss the current understanding of MDSCs within the context of specific traumatic injury types and sepsis. To improve delineation of their functional role, we propose a systemic approach to MDSC analysis including phenotypic standardization, longitudinal analysis, and expansion of clinical research.

Identification of unique microRNA expression patterns in bone marrow hematopoietic stem and progenitor cells after hemorrhagic shock and multiple injuries in young and old adult mice

BACKGROUND

After severe trauma, the older host experiences more dysfunctional hematopoiesis of bone marrow (BM) hematopoietic stem and progenitor cells (HSPCs), and dysfunctional differentiation of circulating myeloid cells into effective innate immune cells. Our main objective was to compare BM HSPC microRNA (miR) responses of old and young mice in a clinically relevant model of severe trauma and shock.

METHODS

C57BL/6 adult male mice aged 8 to 12 weeks (young) and 18 to 24 months (old) underwent multiple injuries and hemorrhagic shock (polytrauma [PT]) that engenders the equivalent of major trauma (Injury Severity Score, >15). Pseudomonas pneumonia (PNA) was induced in some young and old adult mice 24 hours after PT. MicroRNA expression patterns were determined from lineage-negative enriched BM HSPCs isolated from PT and PT-PNA mice at 24 and 48 hours postinjury, respectively. Genome-wide expression and pathway analyses were also performed on bronchoalveolar lavage (BAL) leukocytes from both mouse cohorts.

RESULTS

MicroRNA expression significantly differed among all experimental conditions (p < 0.05), except for old-naive versus old-injured (PT or PT-PNA) mice, suggesting an inability of old mice to mount a robust early miR response to severe shock and injury. In addition, young adult mice had significantly more leukocytes obtained from their BAL, and there were greater numbers of polymorphonuclear cells compared with old mice (59.8% vs. 2.2%, p = 0.0069). Despite increased gene expression changes, BAL leukocytes from old mice demonstrated a more dysfunctional transcriptomic response to PT-PNA than young adult murine BAL leukocytes, as reflected in predicted upstream functional pathway analysis.

CONCLUSION

The miR expression pattern in BM HSPCs after PT (+/-PNA) is dissimilar in old versus young adult mice. In the acute postinjury phase, old adult mice are unable to mount a robust miR HSPC response. Hematopoietic stem and progenitor cell miR expression in old PT mice reflects a diminished functional status and a blunted capacity for terminal differentiation of myeloid cells.

Macrophage-Derived MicroRNA-21 Drives Overwhelming Glycolytic and Inflammatory Response during Sepsis via Repression of the PGE2/IL-10 Axis

Myeloid cells are critical for systemic inflammation, microbial control, and organ damage during sepsis. MicroRNAs are small noncoding RNAs that can dictate the outcome of sepsis. The role of myeloid-based expression of microRNA-21 (miR-21) in sepsis is inconclusive. In this study, we show that sepsis enhanced miR-21 expression in both peritoneal macrophages and neutrophils from septic C57BL/6J mice, and the deletion of miR-21 locus in myeloid cells (miR-21Δmyel mice) enhanced animal survival, decreased bacterial growth, decreased systemic inflammation, and decreased organ damage. Resistance to sepsis was associated with a reduction of aerobic glycolysis and increased levels of the anti-inflammatory mediators PGE2 and IL-10 in miR-21Δmyel in vivo and in vitro. Using blocking Abs and pharmacological tools, we discovered that increased survival and decreased systemic inflammation in septic miR-21Δmyel mice is dependent on PGE2/IL-10-mediated inhibition of glycolysis. Together, these findings demonstrate that expression of miR-21 in myeloid cells orchestrates the balance between anti-inflammatory mediators and metabolic reprogramming that drives cytokine storm during sepsis.

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.

Context-Dependent miR-21 Regulation of TLR7-Mediated Autoimmune and Foreign Antigen-Driven Antibody-Forming Cell and Germinal Center Responses

MicroRNAs (miRNAs) are involved in healthy B cell responses and the loss of tolerance in systemic lupus erythematosus (SLE), although the role of many miRNAs remains poorly understood. Dampening miR-21 activity was previously shown to reduce splenomegaly and blood urea nitrogen levels in SLE-prone mice, but the detailed cellular responses and mechanism of action remains unexplored. In this study, using the TLR7 agonist, imiquimod-induced SLE model, we observed that loss of miR-21 in Sle1b mice prevented the formation of plasma cells and autoantibody-producing Ab-forming cells (AFCs) without a significant effect on the magnitude of the germinal center (GC) response. We further observed reduced dendritic cell and monocyte numbers in the spleens of miR-21-deficient Sle1b mice that were associated with reduced IFN, proinflammatory cytokines, and effector CD4⁺ T cell responses. RNA sequencing analysis on B cells from miR-21-deficient Sle1b mice revealed reduced activation and response to IFN, and cytokine and target array analysis revealed modulation of numerous miR-21 target genes in response to TLR7 activation and type I IFN stimulation. Our findings in the B6.Sle1bYaa (Sle1b ^Yaa) spontaneous model recapitulated the miR-21 role in TLR7-induced responses with an additional role in autoimmune GC and T follicular helper responses. Finally, immunization with T-dependent Ag revealed a role for miR-21 in foreign Ag-driven GC and Ab, but not AFC, responses. Our data suggest a potential multifaceted, context-dependent role for miR-21 in autoimmune and foreign Ag-driven AFC and GC responses. Further study is warranted to delineate the cell-intrinsic requirements and mechanisms of miR-21 during infection and SLE development.

Long non-coding RNA TUG1 promotes airway remodeling and mucus production in asthmatic mice through the microRNA-181b/HMGB1 axis

MicroRNA-181b (miR-181b) has been well noted with anti-inflammatory properties in several pathological conditions. It has also been suggested to be downregulated in patients with asthma. In this study, we explored the function of miR-181b in airway remodeling in asthmatic mice and the molecular mechanism. A mouse model with asthma was induced by ovalbumin (OVA) challenge, and miR-181b was found to be downregulated in lung tissues in the OVA-challenged mice. Overexpression of miR-181b was introduced in mice, after which the respiratory resistance, inflammatory infiltration, mucus production, and epithelial-mesenchymal transition (EMT) and fibrosis in mouse airway tissues were decreased. The integrated bioinformatics analysis suggested long non-coding RNA (lncRNA) TUG1 as a sponge for miR-181b. miR-181 directly targeted high mobility group box 1 (HMGB1) mRNA. HMGB1 was suggested to enhance activation of the nuclear factor kappa B (NF-κB) signaling. Further upregulation of lncRNA TUG1 blocked the protective functions of miR-181b in asthmatic mice. To conclude, this study evidenced that lncRNA TUG1 reinforces HMGB1 expression through sequestering microRNA-181b, which activates the NF-κB signaling pathway and promotes airway remodeling in asthmatic mice. This study may provide novel ideas in asthma management.

Effect of forkhead box O1 in renal tubular epithelial cells on endotoxin-induced acute kidney injury

Mitochondrial damage in renal tubular epithelial cells (RTECs) is a hallmark of endotoxin-induced acute kidney injury (AKI). Forkhead box O1 (FOXO1) is responsible for regulating mitochondrial function and is involved in several kidney diseases. Here, we investigated the effect of FOXO1 on endotoxin-induced AKI and the related mechanism. In vivo, FOXO1 downregulation in mouse RTECs and mitochondrial damage were found in endotoxin-induced AKI. Overexpression of FOXO1 by kidney focal adeno-associated virus (AAV) delivery improved renal function and reduced mitochondrial damage. Peroxisome proliferator-activated receptor-γ coactivator 1-α (PGC1-α), a master regulator of mitochondrial biogenesis and function, was reduced in endotoxin-induced AKI, but the reduction was reversed by FOXO1 overexpression. In vitro, exposure to LPS led to a decline in HK-2 cell viability, mitochondrial fragmentation, and mitochondrial superoxide accumulation, as well as downregulation of FOXO1, PGC1-α, and mitochondrial complex I/V. Moreover, overexpression of FOXO1 in HK-2 cells increased HK-2 cell viability and PGC1-α expression, and it alleviated the mitochondrial injury and superoxide accumulation induced by LPS. Meanwhile, inhibition of FOXO1 in HK-2 cells by siRNA treatment decreased PGC1-α expression and HK-2 cell viability. Chromatin immunoprecipitation assays and PCR analysis confirmed that FOXO1 bound to the PGC1-α promoter in HK-2 cells. In conclusion, downregulation of FOXO1 in RTECs mediated endotoxin-induced AKI and mitochondrial damage. Overexpression of FOXO1 could improve renal injury and mitochondrial dysfunction, and this effect occurred at least in part as a result of PGC1-α signaling. FOXO1 might be a potential target for the prevention and treatment of endotoxin-induced AKI.

MicroRNAs: future biomarkers and targets of therapy in asthma?

PURPOSE OF REVIEW

MicroRNAs (miRNAs) are small noncoding RNA molecules that are considered one of the fundamental regulatory mechanisms of gene expression. They are involved in many biologic processes, such as signal transduction, cell proliferation and differentiation, apoptosis and stress responses. The purpose of this review is to present recent knowledge about the role of miRNAs in asthma and outline possible applications of miRNAs.

RECENT FINDINGS

A core set of miRNAs involved in asthma includes downregulated let-7 family, miR-193b, miR-375 as well as upregulated miR-21, miR-223, miR-146a, miR-142-5p, miR-142-3p, miR-146b and miR-155. Recently it has been shown that most of the involved miRNAs increase secretion of Th2 cytokines, decrease secretion of Th1 cytokines, promote differentiation of T cells towards Th2 or play a role in hyperplasia and hypertrophy of bronchial smooth muscle cells. The profiles of miRNAs correlate with clinical characteristics, including lung function, phenotype and severity of asthma.

SUMMARY

Recent publications confirmed crucial regulatory role of miRNAs in the pathomechanism of asthma. Some single miRNAs or their sets hold the promise for their use as asthma biomarkers facilitating diagnosis or prediction of treatment outcomes. They are also possible target of future therapies. The studies in this field are lacking though.

Exosomal miR-21 secreted by IL-1β-primed-mesenchymal stem cells induces macrophage M2 polarization and ameliorates sepsis

Sepsis occurs due to a damaging host response to infection and is the chief cause of death in most intensive care units. Mesenchymal stem cells (MSCs) exhibit immunomodulatory properties and can modulate key cells of the innate and adaptive immune systems through various effector mechanisms, such as exosomes. Exosomes and their microRNA (miRNA or miR) cargo including miR-21 can initiate profound phenotypic changes in the tumor microenvironment due to their intercellular communication transmitting the pleiotropic messages between different cell types, tissues, and body fluids. Here, we aimed to characterize the effect of miR-21 delivered from MSC-derived exosomes on the polarization of macrophages in a mouse sepsis model. First, we isolated exosomes from interleukin-1β (IL-1β)-pretreated murine MSCs (βMSCs) and injected them into cecal ligation and puncture (CLP) septic models. We found that βMSCs-derived exosomes could more effectively induce M2-like polarization of macrophages in vitro and in vivo. Administration of βMSCs-derived exosomes attenuated the symptoms in septic mice more effectively and increased their survival rate as compared to exosomes released by naïve MSCs. Importantly, we found that miR-21 was abundantly upregulated in MSCs upon IL-1β stimulation and packaged into exosomes. This exosomal miR-21 was transferred to macrophages, leading to M2 polarization in vitro and in vivo. The therapeutic efficacy of βMSC-derived exosomes was partially lost upon miR-21 inhibition by its specific inhibitors. More specifically, we demonstrated βMSCs-derived exosomes inhibited the effects of PDCD4, the target gene of miR-21, on macrophage polarization and sepsis. In conclusion, exosomal miR-21 emerged as a key mediator of IL-1β pretreatment induced immunomodulatory properties of MSCs. The study indicated a novel basis for therapeutic application of MSCs in sepsis.

A bird's eye view of the advanced approaches and strategies for overshadowing triple negative breast cancer

Triple negative breast cancer (TNBC) is one of the most aggressive form of breast cancer. It is characterized by the absence of estrogen, progesterone and human epidermal growth factor receptors. The main issue with TNBC is that it exhibits poor prognosis, high risk of relapse, short progression-free survival and low overall survival in patients. This is because the conventional therapy used for managing TNBC has issues pertaining to poor bioavailability, lower cellular uptake, increased off-target effects and development of resistance. To overcome such pitfalls, several other approaches are explored. In this context, the present manuscript showcases three of the most widely used approaches which are (i) nanotechnology-based approach; (ii) gene therapy approach and (iii) Phytochemical-based approach. The ultimate focus is to present and explain the insightful reports based on these approaches. Further, the review also expounds on the identified molecular targets and novel targeting ligands which are explored for managing TNBC effectively. Thus, in a nutshell, the review tries to highlight these existing treatment approaches which might inspire for future development of novel therapies with a potential of overshadowing TNBC.

Identification and Validation of Potential miRNAs, as Biomarkers for Sepsis and Associated Lung Injury: A Network-Based Approach

Sepsis is a dysregulated immune response disease affecting millions worldwide. Delayed diagnosis, poor prognosis, and disease heterogeneity make its treatment ineffective. miRNAs are imposingly involved in personalized medicine such as therapeutics, due to their high sensitivity and accuracy. Our study aimed to reveal the biomarkers that may be involved in the dysregulated immune response in sepsis and lung injury using a computational approach and in vivo validation studies. A sepsis miRNA Gene Expression Omnibus (GEO) dataset based on the former analysis of blood samples was used to identify differentially expressed miRNAs (DEMs) and associated hub genes. Sepsis-associated genes from the Comparative Toxicogenomics Database (CTD) that overlapped with identified DEM targets were utilized for network construction. In total, 317 genes were found to be regulated by 10 DEMs (three upregulated, namely miR-4634, miR-4638-5p, and miR-4769-5p, and seven downregulated, namely miR-4299, miR-451a, miR181a-2-3p, miR-16-5p, miR-5704, miR-144-3p, and miR-1290). Overall hub genes (HIP1, GJC1, MDM4, IL6R, and ERC1) and for miR-16-5p (SYNRG, TNRC6B, and LAMTOR3) were identified based on centrality measures (degree, betweenness, and closeness). In vivo validation of miRNAs in lung tissue showed significantly downregulated expression of miR-16-5p corroborating with our computational findings, whereas expression of miR-181a-2-3p and miR-451a were found to be upregulated in contrast to the computational approach. In conclusion, the differential expression pattern of miRNAs and hub genes reported in this study may help to unravel many unexplored regulatory pathways, leading to the identification of critical molecular targets for increased prognosis, diagnosis, and drug efficacy in sepsis and associated organ injuries.

JAK/STAT signaling pathway-mediated microRNA-181b promoted blood-brain barrier impairment by targeting sphingosine-1-phosphate receptor 1 in septic rats

Background

Blood-brain barrier (BBB) impairment plays a significant role in the pathogenesis of sepsis-associated encephalopathy (SAE). However, the molecular mechanisms are poorly understood. In the present study, we aimed to investigate the regulatory relationship between the Janus kinase/signal transducers and activators of transcription (JAK/STAT) signaling pathway, microRNA (miR)-181b and its target genes in sepsis in vivo and in vitro.

Methods

Four rat models (sham, sepsis, sepsis plus STAT3 inhibitor (Stattic), and sepsis plus miR-181b inhibitor [sepsis + anta-miR-181b]) were established. For the in vitro experiments, rat brain microvascular endothelial cells (rBMECs) and rat brain astrocytes (rAstrocytes) were cultured with 10% serum harvested from sham, sepsis, and sepsis + anta-miR-181b rats. Chromatin immunoprecipitation-quantitative polymerase chain reaction (ChIP-QPCR) analysis was carried out to detect the binding and enrichment of the JAK/STAT3 signal core transcription complex in the miR-181b promoter region. Dual-luciferase reporter gene assay was conducted to test miR-181b and its target genes. The cell adhesion rate of rBMECs was also measured.

Results

During our investigations, the expression levels of miR-181b, p-JAK2, p-STAT3, and C/EBPβ were found to be significantly increased in the septic rats compared with the sham rats. STAT3 inhibitor halted BBB damage by downregulating the expression of miR-181b. In addition, miR-181b targeted sphingosine-1-phosphate receptor 1 (S1PR1) and neurocalcin delta (NCALD). The up-regulated miR-181b significantly decreased the cell adhesion rate of rBMECs. The administration of miR-181b inhibitor reduced damage to the BBB through increasing the expression of S1PR1 and NCALD, which again proved that miR-181b negatively regulates SIPR1 and NCALD to induce BBB damage.

Conclusions

Our study demonstrated that JAK2/STAT3 signaling pathway induced expression of miR-181b, which promoted BBB impairment in rats with sepsis by downregulating S1PR1 and decreasing BBB cell adhesion. These findings strongly suggest JAK2/STAT3/miR-181b axis as therapeutic target in protecting against sepsis-induced BBB damage.

High mobility group nucleosomal binding 2 reduces integrin α5/β1-mediated adhesion of Klebsiella pneumoniae on human pulmonary epithelial cells via nuclear factor I

It has been reported that high mobility group nucleosomal binding domain 2 (HMGN2) is a nucleus-related protein that regulates gene transcription and plays a critical role in bacterial clearance. An elevated level of HMGN2 reduced integrin α5/β1 expression of human pulmonary epithelial A549 cells was demonstrated during Klebsiella pneumoniae infection, thus weakening bacterial adhesion and invasion. However, the mechanism by which HMGN2 regulates integrin expression remains unclear. This study found that a transcription factor-nuclear factor I (NFI), which serves as the potential target of HMGN2 regulated integrin expression. The results showed that HMGN2 was able to promote NFIA and NFIB expression by increasing H3K27 acetylation of NFIA/B promoter regions. The integrin α5/β1 expression was significantly enhanced by knockdown of NFIA/B via a siRNA approach. Meanwhile, NFIA/B silence could also compromise the inhibition effect of HMGN2 on the integrin α5/β1 expression. Mechanistically, it was demonstrated that HMGN2 facilitated the recruitment of NFI on the promoter regions of integrin α5/β1 according to the chromatin immunoprecipitation assay. In addition, it was further demonstrated that the knockdown of NFIA/B induced more adhesion of Klebsiella pneumoniae on pulmonary epithelial A549 cells, which could be reversed by the application of an integrin inhibitor RGD. The results revealed a regulatory role of HMGN2 on the transcription level of integrin α5/β1, indicating a potential treatment strategy against Klebsiella pneumoniae-induced infectious lung diseases.

MicroRNAs and lncRNAs-A New Layer of Myeloid-Derived Suppressor Cells Regulation

Myeloid-derived suppressor cells (MDSCs) constitute an important component in regulating immune responses in several abnormal physiological conditions such as cancer. Recently, novel regulatory tumor MDSC biology modulating mechanisms, including differentiation, expansion and function, were defined. There is growing evidence that miRNAs and long non-coding RNAs (lncRNA) are involved in modulating transcriptional factors to become complex regulatory networks that regulate the MDSCs in the tumor microenvironment. It is possible that aberrant expression of miRNAs and lncRNA contributes to MDSC biological characteristics under pathophysiological conditions. This review provides an overview on miRNAs and lncRNAs epiregulation of MDSCs development and immunosuppressive functions in cancer.

Non-coding RNAs and Exosomes: Their Role in the Pathogenesis of Sepsis

Sepsis is characterized as an uncontrolled host response to infection, and it represents a serious health challenge, causing excess mortality and morbidity worldwide. The discovery of sepsis-related epigenetic and molecular mechanisms could result in improved diagnostic and therapeutic approaches, leading to a reduced overall risk for affected patients. Accumulating data show that microRNAs, non-coding RNAs, and exosomes could all be considered as novel diagnostic markers for sepsis patients. These biomarkers have been demonstrated to be involved in regulation of sepsis pathophysiology. However, epigenetic modifications have not yet been widely reported in actual clinical settings, and further investigation is required to determine their importance in intensive care patients. Further studies should be carried out to explore tissue-specific or organ-specific epigenetic RNA-based biomarkers and their therapeutic potential in sepsis patients.

MALAT1 overexpression attenuates AS by inhibiting ox-LDL-stimulated dendritic cell maturation via miR-155-5p/NFIA axis

MALAT1 is associated with dendritic cells (DCs) maturation in Atherosclerosis (AS). This article aims to demystify the role of MALAT1 in AS. We separated immature DCs (iDCs) from healthy volunteers or ApoE-/- mice. And iDCs were treated with oxidized low density lipoprotein (ox-LDL) to induce DCs maturation. We found that ox-LDL promoted the levels of DCs maturation markers including CD83, CD86, IL-12 and IL-6. MALAT1 and NFIA were down-regulated, whereas miR-155-5p was up-regulated in the ox-LDL-treated iDCs. Furthermore, DCs maturation was notably suppressed by MALAT1 overexpression, NFIA overexpression or miR-155-5p knockdown. Moreover, MALAT1 functioned as a competing endogenous RNA to repress miR-155-5p, which controlled its down-stream target, NFIA. In addition, MALAT1 overexpression inhibited ox-LDL-stimulated DCs maturation by regulating miR-155-5p/NFIA axis. In AS mice, MALAT1 overexpression attenuated ox-LDL-stimulated DCs maturation and reduced atherosclerotic plaque area. In summary, our study demonstrates that MALAT1 overexpression attenuates AS by inhibiting ox-LDL-stimulated DCs maturation via miR-155-5p/NFIA axis. Thus, MALAT1/miR-155-5p/NFIA axis can potentially be used in the treatment of AS.

Circular RNAs in Sepsis: Biogenesis, Function, and Clinical Significance

Sepsis is a life-threatening condition that occurs when the body responds to an infection that damages it is own tissues. The major problem in sepsis is rapid, vital status deterioration in patients, which can progress to septic shock with multiple organ failure if not properly treated. As there are no specific treatments, early diagnosis is mandatory to reduce high mortality. Despite more than 170 different biomarkers being postulated, early sepsis diagnosis and prognosis remain a challenge for clinicians. Recent findings propose that circular RNAs (circRNAs) may play a prominent role in regulating the patients’ immune system against different pathogens, including bacteria and viruses. Mounting evidence also suggests that the misregulation of circRNAs is an early event in a wide range of diseases, including sepsis. Despite circRNA levels being altered in sepsis, the specific mechanisms controlling the dysregulation of these noncoding RNAs are not completely elucidated, although many factors are known to affect circRNA biogenesis. Therefore, there is a need to explore the molecular pathways that lead to this disorder. This review describes the role of this new class of regulatory RNAs in sepsis and the feasibility of using circRNAs as diagnostic biomarkers for sepsis, opening up new avenues for circRNA-based medicine.

HuR promotes miRNA-mediated upregulation of NFI-A protein expression in MDSCs during murine sepsis

Myeloid-derived suppressor cells (MDSCs) contribute to high mortality rates during sepsis, but how sepsis induces MDSCs is unclear. Previously we reported that microRNA (miR)-21 and miR-181b reprogram MDSCs in septic mice by increasing levels of DNA binding transcription factor, nuclear factor 1 (NFI-A). Here, we provide evidence that miR-21 and miR-181b stabilize NFI-A mRNA and increase NFI-A protein levels by recruiting RNA-binding proteins HuR and Ago1 to its 3' untranslated region (3'UTR). We also find that the NFI-A GU-rich element (GRE)-binding protein CUGBP1 counters miR-21 and miR-181b dependent NFI-A mRNA stabilization and decreases protein production by replacing 3'UTR bound Ago1 with Ago2. We confirmed the miR-21 and miR-181b dependent reprogramming pathway in MDSCs transfected with a luciferase reporter construct containing an NFI-A 3'UTR fragment with point mutations in the miRNA binding sites. These results suggest that targeting NFI-A in MDSCs during sepsis may enhance resistance to uncontrolled infection.

Epigenetics Mechanisms in Multiorgan Dysfunction Syndrome

Epigenetic mechanisms including deoxyribonucleic acid (DNA) methylation, histone modifications (eg, histone acetylation), and microribonucleic acids (miRNAs) have gained much scientific interest in the last decade as regulators of genes expression and cellular function. Epigenetic control is involved in the modulation of inflammation and immunity, and its dysregulation can contribute to cell damage and organ dysfunction. There is growing evidence that epigenetic changes can contribute to the development of multiorgan dysfunction syndrome (MODS), a leading cause of mortality in the intensive care unit (ICU). DNA hypermethylation, histone deacetylation, and miRNA dysregulation can influence cytokine and immune cell expression and promote endothelial dysfunction, apoptosis, and end-organ injury, contributing to the development of MODS after a critical injury. Epigenetics processes, particularly miRNAs, are emerging as potential biomarkers of severity of disease, organ damage, and prognostic factors in critical illness. Targeting epigenetics modifications can represent a novel therapeutic approach in critical care. Inhibitors of histone deacetylases (HDCAIs) with anti-inflammatory and antiapoptotic activities represent the first class of drugs that reverse epigenetics modifications with human application. Further studies are required to acquire a complete knowledge of epigenetics processes, full understanding of their individual variability, to expand their use as accurate and reliable biomarkers and as safe target to prevent or attenuate MODS in critical disease.

Evaluation of the clinical value of circulating miR-101, miR-187 and miR-21 in neonatal sepsis diagnosis and prognosis

Background

Neonatal sepsis is considered as a complicated syndrome, which requires urgent intervention to avoid the unfavorable outcome. Thus, biomarkers that can either distinguish sepsis early or predict sepsis outcome are of critical need. Therefore, the aim of the current study was to investigate the clinical value of miR-187, miR-101, and miR-21 on neonatal sepsis diagnosis and prediction of prognosis. Fifty neonates with sepsis, 30 neonates with SIRS, and 20 healthy neonates were selected. Relative expression levels of the selected miRNAs were quantified by qRT-PCR. Serum CRP and PCT were analyzed.

Results

miR-101 and miR-187 expression levels were elevated in septic neonates compared with SIRS neonates and normal controls. The AUC of miR-101, miR-187, and PCT to predict sepsis diagnosis were 0.908, 789, and 0.856, respectively. miR-21 expression levels in non-survivors were significantly higher than in survivors. The AUC of miR-21, a score of neonatal acute physiology (SNAP-II), and PCT to detect the predictive mortality value were 0.793, 0.781, and 0.635, respectively. Survival analysis revealed that high miR-21 expression levels were related to low survival rates. miR-21 and SNAP II were independent risk factors for sepsis mortality, and the AUC of the two combined variables’ predictive probabilities was 0.926 and yielded a specificity of 91.2% and a sensitivity of 81.3%, which was higher than that of either miR-21 or SNAP II.

Conclusion

miR-101 might function as a hopeful diagnostic biomarker for neonatal sepsis. Additionally, miR-21 gained attention to be a valuable predictor for sepsis prognosis especially if combined with SNAP II.

Modulation of Immunosuppression by Oligonucleotide-Based Molecules and Small Molecules Targeting Myeloid-Derived Suppressor Cells

Myeloid-derived suppressor cells (MDSCs) are immature myeloid cells that exert suppressive function on the immune response. MDSCs expand in tumor-bearing hosts or in the tumor microenvironment and suppress T cell responses via various mechanisms, whereas a reduction in their activities has been observed in autoimmune diseases or infections. It has been reported that the symptoms of various diseases, including malignant tumors, can be alleviated by targeting MDSCs. Moreover, MDSCs can contribute to patient resistance to therapy using immune checkpoint inhibitors. In line with these therapeutic approaches, diverse oligonucleotide-based molecules and small molecules have been evaluated for their therapeutic efficacy in several disease models via the modulation of MDSC activity. In the current review, MDSC-targeting oligonucleotides and small molecules are briefly summarized, and we highlight the immunomodulatory effects on MDSCs in a variety of disease models and the application of MDSC-targeting molecules for immuno-oncologic therapy.

Ferumoxytol Attenuates the Function of MDSCs to Ameliorate LPS-Induced Immunosuppression in Sepsis

Sepsis-induced immunosuppression is recognized as one of the main features responsible for therapeutic failures. Myeloid-derived suppressor cells (MDSCs), which are mainly characterized by their suppressive properties, have been reported to be expanded in sepsis. Ferumoxytol (FMT), an FDA-approved iron supplement, has been shown to possess immune-modulatory properties in tumors. However, it is unclear whether FMT alters the functions of MDSCs to reduce late-sepsis immunosuppression. Here, we showed an immunomodulatory effect of FMT on MDSCs to ameliorate lipopolysaccharide (LPS)-induced immunosuppression in the late stage of sepsis. Separation of cells with internalized FMT and detection of the intracellular iron content showed that MDSCs could uptake FMT. Low doses of FMT had no effects on the cell viability of MDSCs, but FMT inhibited the expansion of MDSCs in vitro. Moreover, FMT significantly downregulated the expression levels of Arg-1, S100A8, S100A9, and p47phox as well as ROS production in MDSCs. FMT decreased the percentage of granulocytic MDSCs (G-MDSCs) and promoted the differentiation of MDSCs into macrophages. Furthermore, FMT reduced white blood cell recruitment and alveolar wall thickening in the lungs and areas of necrosis in the liver as well as some biochemical markers of liver dysfunction. FMT decreased the percentage of G-MDSCs and monocytic MDSCs (M-MDSCs) in the spleens of LPS-induced septic mice. Of note, FMT reduced the T cell immunosuppressive functions of both G-MDSCs and M-MDSCs. Expectedly, FMT also significantly reduced Arg-1 and p47phox gene expression in splenic CD11b⁺Gr-1⁺ cells isolated from LPS-challenged mice. These data indicate that FMT decreased the immunosuppressive functions of MDSCs by decreasing Arg-1 and ROS production, suggesting that FMT may reduce long-term immunosuppression in the late stage of sepsis.

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

Background

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

Methods

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

Results

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

Conclusions

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

MicroRNAs: Potential Biomarkers and Targets of Therapy in Allergic Diseases?

MicroRNAs (miRNAs) are small non-coding RNA molecules that are 18-22 nucleotides long and highly conserved throughout evolution. Currently, they are considered one of the fundamental regulatory mechanisms of genes expression. It has been demonstrated that miRNAs are involved in many biologic processes, such as signal transduction, cell proliferation and differentiation, apoptosis and stress responses. More recently, the role of miRNA has also been revealed in numerous immunological and inflammatory disorders, including allergic inflammation. Specific miRNA profiles were demonstrated in asthma, allergic rhinitis and atopic dermatitis. A core set of miRNAs involved in atopic diseases include upregulated miR-21, miR-223, miR-146a, miR-142-5p, miR-142-3p, miR-146b, miR-155 and downregulated let-7 family, miR-193b and miR-375. Most of the involved miRNAs increase secretion of Th2 cytokines (miR-1248, miR-146b), decrease secretion of Th1 cytokines (miR-513-5p, miR-625-5p) or promote differentiation of T cells towards Th2 (miR-21, miR-19a). In asthma miR-140-3p, miR-708 and miR-142-3p play a role in hyperplasia and hypertrophy of bronchial smooth muscle cells. Some single miRNAs or, more probably, their sets hold the promise for their use as biomarkers of atopic diseases. They are also promising target of future therapies.

MicroRNA networks regulate the differentiation, expansion and suppression function of myeloid-derived suppressor cells in tumor microenvironment

Myeloid-derived suppressor cells (MDSCs), one heterogeneous population of immature myeloid cells, have suppressive function on immune response during tumor, inflammation, infection and autoimmune diseases. The molecular mechanism underlying expansion and function of MDSCs is becoming appreciated to manipulate immune response in the diseases. MicroRNA (miRNAs) as one short noncoding RNAs, are involved in regulating cell proliferation, differentiation and maturation. However, it needs to be further studied how miRNAs mediate the development and function of MDSC in association with cancer and other diseases. In the review, we report and discuss recent studies that miRNAs networks regulate the differentiation, expansion and suppression function of MDSCs in tumor microenvironment or other diseases through different signaling pathways. Those studies may provide one novel potential approach for tumor immunotherapy.

Epigenetics in Sepsis: Understanding Its Role in Endothelial Dysfunction, Immunosuppression, and Potential Therapeutics

Sepsis has a complex pathophysiology in which both excessive and refractory inflammatory responses are hallmark features. Pro-inflammatory cytokine responses during the early stages are responsible for significant endothelial dysfunction, loss of endothelial integrity, and organ failure. In addition, it is now well-established that a substantial number of sepsis survivors experience ongoing immunological derangement and immunosuppression following a septic episode. The underpinning mechanisms of these phenomena are incompletely understood yet they contribute to a significant proportion of sepsis-associated mortality. Epigenetic mechanisms including DNA methylation, histone modifications, and non-coding RNAs, have an increasingly clear role in modulating inflammatory and other immunological processes. Recent evidence suggests epigenetic mechanisms are extensively perturbed as sepsis progresses, and particularly play a role in endothelial dysfunction and immunosuppression. Whilst therapeutic modulation of the epigenome is still in its infancy, there is substantial evidence from animal models that this approach could reap benefits. In this review, we summarize research elucidating the role of these mechanisms in several aspects of sepsis pathophysiology including tissue injury and immunosuppression. We also evaluate pre-clinical evidence for the use of "epi-therapies" in the treatment of poly-microbial sepsis.

Silencing of miR-486 alleviates LPS-stimulated inflammatory response of macrophages through targeting SIRT1

Previous studies identified that microRNAs (miRNAs) have promising diagnostic and prognostic value against sepsis. MiR-486 was demonstrated to be upregulated in sepsis. However, the detailed role and underlying mechanism of miR-486 in the inflammatory response of sepsis are still unclear. In this research, macrophages were stimulated with lipopolysaccharide (LPS) to establish a sepsis model in vitro. qRT-PCR was used to detect miR-486 expression and the mRNA levels of sirtuin (SIRT1), tumor necrosis factor (TNF)-α, interleukin (IL)-6 and IL-1β. ELISA assay was performed to measure the levels of TNF-α, IL-6 and IL-1β. SIRT1 protein expression was determined by Western blot analysis. The targeted relationship of miR-486 and SIRT1 was confirmed by dual-luciferase reporter assay. Our data supported that miR-486 was upregulated in the serum of sepsis patients. MiR-486 expression and inflammatory response were elevated by LPS stimulation in macrophages. MiR-486 silencing or SIRT1 overexpression alleviated inflammatory response in LPS-stimulated macrophages. Moreover, SIRT1 was a direct target of miR-486. Anti-miR-486-mediated anti-inflammatory response in LPS-stimulated macrophages was antagonized by SIRT1 inhibition. Our data suggested that miR-486 silencing alleviated inflammatory response in macrophages under LPS stimulation at least partly through targeting SIRT1. Targeting miR-486 may provide a novel way to protect against dysregulated inflammatory response in sepsis patients.

S100A9 maintains myeloid-derived suppressor cells in chronic sepsis by inducing miR-21 and miR-181b

Myeloid-derived suppressor cells (MDSC) expand during sepsis, suppress both innate and adaptive immunity, and promote chronic immunosuppression, which characterizes the late/chronic phase of sepsis. We previously reported that the transcription factors Stat3 and C/EBPβ synergize to induces the expression of microRNA (miR)-21 and miR-181b to promote MDSC expansion in a mouse model of polymicrobial sepsis that progresses from an early/acute proinflammatory phase to a late/chronic immunosuppressive stage. We also showed that Gr1⁺CD11b⁺ cells, the precursors of MDSCs, from mice genetically deficient in the inflammatory protein S100A9 lack miR-21 or miR-181b in late sepsis, and are not immunosuppressive. In the present study, we show that S100A9 induces miR-21 and miR-181b during the late sepsis phase. We find that S100A9 associates with and stabilizes the Stat3-C/EBPβ protein complex that activates the miRNA promoters. Reconstituting Gr1⁺CD11b⁺ cells from S100A9 knockout mice with late sepsis with S100A9 protein restores the Stat3-C/EBPβ protein complex and miRNA expressions, and switches the Gr1⁺CD11b⁺ cells into the immunosuppressive, MDSC phenotype. Importantly, we find that this process requires IL-10 mediated signaling, which induces S100A9 translocation from the cytosol to the nucleus. These results demonstrate that S100A9 promotes MDSC expansion and immunosuppression in late/chronic sepsis by inducing the expression of miR-21 and miR-181b.

Myeloid-Derived Suppressor Cells in Sepsis

Myeloid-derived suppressor cells (MDSCs) are immature myeloid cells characterized by their immunosuppressive functions. MDSCs expand during chronic and acute inflammatory conditions, the best described being cancer. Recent studies uncovered an important role of MDSCs in the pathogenesis of infectious diseases along with sepsis. Here we discuss the mechanisms underlying the expansion and immunosuppressive functions of MDSCs, and the results of preclinical and clinical studies linking MDSCs to sepsis pathogenesis. Strikingly, all clinical studies to date suggest that high proportions of blood MDSCs are associated with clinical worsening, the incidence of nosocomial infections and/or mortality. Hence, MDSCs are attractive biomarkers and therapeutic targets for sepsis, especially because these cells are barely detectable in healthy subjects. Blocking MDSC-mediated immunosuppression and trafficking or depleting MDSCs might all improve sepsis outcome. While some key aspects of MDSCs biology need in depth investigations, exploring these avenues may participate to pave the way toward the implementation of personalized medicine and precision immunotherapy for patients suffering from sepsis.