Role of Wnt signaling during inflammation and sepsis: A review of the literature

Soluble vascular endothelial glycocalyx proteoglycans as potential therapeutic targets in inflammatory diseases

Reducing the activity of cytokines and leukocyte extravasation is an emerging therapeutic strategy to limit tissue-damaging inflammatory responses and restore immune homeostasis in inflammatory diseases. Proteoglycans embedded in the vascular endothelial glycocalyx, which regulate the activity of cytokines to restrict the inflammatory response in physiological conditions, are proteolytically cleaved in inflammatory diseases. Here we critically review the potential of proteolytically shed, soluble vascular endothelial glycocalyx proteoglycans to modulate pathological inflammatory responses. Soluble forms of the proteoglycans syndecan-1, syndecan-3 and biglycan exert beneficial anti-inflammatory effects by the removal of chemokines, suppression of proinflammatory cytokine expression and leukocyte migration, and induction of autophagy of proinflammatory M1 macrophages. By contrast, soluble versikine and decorin enhance proinflammatory responses by increasing inflammatory cytokine synthesis and leukocyte migration. Endogenous syndecan-2 and mimecan exert proinflammatory effects, syndecan-4 and perlecan mediate beneficial anti-inflammatory effects and glypican regulates Hh and Wnt signaling pathways involved in systemic inflammatory responses. Taken together, targeting the vascular endothelial glycocalyx-derived, soluble syndecan-1, syndecan-2, syndecan-3, syndecan-4, biglycan, versikine, mimecan, perlecan, glypican and decorin might be a potential therapeutic strategy to suppress overstimulated cytokine and leukocyte responses in inflammatory diseases.

LGK974 suppresses the formation of deep vein thrombosis in mice with sepsis

BACKGROUND

Sepsis is a disorder characterized by host inflammation and is caused by systemic infection. The inflammatory cytokine storm results in platelet overactivation, leading to coagulation dysfunction and thrombosis, but the underlying mechanism remains poorly understood. Recent evidence has shown that the Wnt/β-catenin signaling pathway is related to sepsis, but its role and mechanism in sepsis complicated with deep vein thrombosis (DVT) are unclear.

METHODS

In this study, a cecal ligation and puncture (CLP)-induced sepsis model and DVT mouse model were constructed by inferior vena cava ligation. The levels of serum inflammatory factors and adhesion molecules were measured in each group, and the thrombus weight and size, hematoxylin-eosin staining, collagen fiber tissue, and transcriptome of the venous wall were analyzed. The activation of the Wnt/β-catenin signal was evaluated by quantitative real-time polymerase chain reaction, Western blotting, ELISA, and immunohistochemical and immunofluorescence methods.

RESULTS

Sepsis significantly promoted the formation of venous wall collagen fibers and DVT. In addition, Porcn significantly upregulated and activated the Wnt/β-catenin signaling pathway in sepsis mouse models with DVT. In contrast, the Wnt signaling inhibitor LGK974 was found to improve the survival rate, decrease thrombosis, and inhibit the expression of inflammation and adhesion molecules in sepsis mice with DVT. Therefore, activation of the Wnt/β-catenin signal may promote the formation of DVT in sepsis mice.

CONCLUSIONS

LGK974 protects against DVT formation in sepsis mice by inhibiting the activation of the Wnt/β-catenin signal and down-regulating the production of proinflammatory cytokines, PAI-1, and adhesion molecules. LGK974 may be a new candidate for the treatment of sepsis complicated with DVT.

TCF1/LEF1 triggers Wnt-dependent chemokine/cytokine-induced inflammation and cadherin pathways to drive T-ALL cell migration

T-cell acute lymphoblastic leukemia (T-ALL) is a type of aggressive hematologic malignancy. It progresses quickly and it is likely to be fatal within a few months without treatment. Despite the limitations of current clinical therapies, there is an urgent need for novel and targeted therapies. To explore potential targeted therapies, molecular genetic mechanisms of T-ALL metastasis must be uncovered. However, the genes and mechanisms that mediate T-ALL metastasis are largely unknown. Recent insights into T-ALL biology have identified several genes that can be grouped into several targetable signaling pathways. The Wnt/β-catenin signaling pathway is one of the most important pathways. Our work investigated the functions of TCF1 and LEF1 in cell growth and migration mediated by the Wnt signaling pathway. We found that TCF1 and LEF1 knockdown weakly repressed T-ALL cell proliferation but distinctly impaired cell migration. T-ALL metastasis is dependent on cell migration and invasion. Our results displayed that TCF1 and LEF1 regulated T-ALL cell migration by the Wnt-dependent chemokine and cytokine-induced inflammation and cadherin signaling pathways. By transcriptionally regulating these pathways-associated genes, TCF1 and LEF1 inhibited cell adhesion and promoted cell migration and invasion.

Telomere Length and Telomerase Activity in Subcutaneous and Visceral Adipose Tissues from Obese and Non-Obese Patients with and without Colorectal Cancer

To investigate the molecular mechanisms that link obesity and colorectal cancer (CRC), we analyzed parameters related to telomere function in subcutaneous and visceral adipose tissues (SAT and VAT), including subjects with and without CRC, who were classified according to their body mass index (BMI). Adipose tissues were obtained from 147 patients who had undergone surgery. A total of 66 cases corresponded to CRC patients, and 81 subjects were not affected by cancer. Relative telomere length was established by qPCR, and telomerase activity was determined by a method based on the telomeric repeat amplification protocol. Our results indicated longer telomeres in patients affected by CRC, both in SAT and VAT, when compared to the group of subjects without CRC. Tumor local invasion was associated with telomere length (TL) in SAT. Considering the BMI values, significant differences were found in the TL of both adipose tissues between subjects affected by CRC and those without cancer. Overweight subjects showed the greatest differences, with longer telomeres in the group of CRC patients, and a higher number of cases with telomerase reactivation in the VAT of subjects without cancer. In conclusion, parameters related to telomere function in adipose tissue could be considered as potential biomarkers in the evaluation of CRC and obesity.

Efficacy of Clinically Used PARP Inhibitors in a Murine Model of Acute Lung Injury

Poly(ADP-ribose) polymerase 1 (PARP1), as a potential target for the experimental therapy of acute lung injury (ALI), was identified over 20 years ago. However, clinical translation of this concept was not possible due to the lack of clinically useful PARP inhibitors. With the clinical introduction of several novel, ultrapotent PARP inhibitors, the concept of PARP inhibitor repurposing has re-emerged. Here, we evaluated the effect of 5 clinical-stage PARP inhibitors in oxidatively stressed cultured human epithelial cells and monocytes in vitro and demonstrated that all inhibitors (1-30 µM) provide a comparable degree of cytoprotection. Subsequent in vivo studies using a murine model of ALI compared the efficacy of olaparib and rucaparib. Both inhibitors (1-10 mg/kg) provided beneficial effects against lung extravasation and pro-inflammatory mediator production-both in pre- and post-treatment paradigms. The underlying mechanisms include protection against cell dysfunction/necrosis, inhibition of NF-kB and caspase 3 activation, suppression of the NLRP3 inflammasome, and the modulation of pro-inflammatory mediators. Importantly, the efficacy of PARP inhibitors was demonstrated without any potentiation of DNA damage, at least as assessed by the TUNEL method. These results support the concept that clinically approved PARP inhibitors may be repurposable for the experimental therapy of ALI.

Blockade of Wnt Secretion Attenuates Myocardial Ischemia-Reperfusion Injury by Modulating the Inflammatory Response

Wnt (a portmanteau of Wingless and Int-1) signaling in the adult heart is largely quiescent. However, there is accumulating evidence that it gets reactivated during the healing process after myocardial infarction (MI). We here tested the therapeutic potential of the Wnt secretion inhibitor LGK-974 on MI healing. Ischemia/reperfusion (I/R) injury was induced in mice and Wnt signaling was inhibited by oral administration of the porcupine inhibitor LGK-974. The transcriptome was analyzed from infarcted tissue by using RNA sequencing analysis. The inflammatory response after I/R was evaluated by flow cytometry. Heart function was assessed by echocardiography and fibrosis by Masson's trichrome staining. Transcriptome and gene set enrichment analysis revealed a modulation of the inflammatory response upon administration of the Wnt secretion inhibitor LGK-974 following I/R. In addition, LGK-974-treated animals showed an attenuated inflammatory response and improved heart function. In an in vitro model of hypoxic cardiomyocyte and monocyte/macrophage interaction, LGK974 inhibited the activation of Wnt signaling in monocytes/macrophages and reduced their pro-inflammatory phenotype. We here show that Wnt signaling affects inflammatory processes after MI. The Wnt secretion inhibitor LGK-974 appears to be a promising compound for future immunomodulatory approaches to improve cardiac remodeling after MI.

Canonical Wnt signaling enhances pro-inflammatory response to titanium by macrophages

Biomaterial characteristics like surface roughness and wettability can determine the phenotype of macrophages following implantation. We have demonstrated that inhibiting Wnt ligand secretion abolishes macrophage polarization in vitro and in vivo; however, the role of canonical Wnt signaling in macrophage activation in response to physical and chemical biomaterial cues is unknown. The aim of this study was to understand whether canonical Wnt signaling affects the response of macrophages to titanium (Ti) surface roughness or wettability in vitro and in vivo. Activating canonical Wnt signaling increased expression of toll-like receptors and interleukin receptors and secreted pro-inflammatory cytokines and reduced anti-inflammatory cytokines on Ti, regardless of surface properties. Inhibiting canonical Wnt signaling reduced pro-inflammatory cytokines on all Ti surfaces and increased anti-inflammatory cytokines on rough or rough-hydrophilic Ti. In vivo, activating canonical Wnt signaling increased total macrophages, pro-inflammatory macrophages, and T cells and decreased anti-inflammatory macrophages on both smooth and rough-hydrophilic implants. Functionally, canonical Wnt activation increases pro-inflammatory macrophage response to cell and cell-extracellular matrix lysates. These results demonstrate that activating canonical Wnt signaling primes macrophages to a pro-inflammatory phenotype that affects their response to Ti implants in vitro and in vivo.

Synbiotic Supplementation Modulates Gut Microbiota, Regulates β-Catenin Expression and Prevents Weight Gain in ob/ob Mice: Preliminary Findings

Background: Obesity is one of the main health problems in the world today, and dysbiosis seems to be one of the factors involved. The aim of this study was to examine the impact of synbiotic supplementation on obesity and the microbiota in ob/ob mice. Twenty animals were divided into four groups: obese treated (OT), obese control (OC), lean treated (LT) and lean control (LC). All animals received a standard diet for 8 weeks. The treated groups received a synbiotic (Simbioflora-Invictus Farmanutrição Ltd., Sao Paulo, Brazil) in water, while the nontreated groups received only water. After 8 weeks, all animals were sacrificed, and gut tissue and stool samples were collected for mRNA isolation and microbiota analysis, respectively. β-Catenin, occludin, cadherin and zonulin in the gut tissue were analyzed via RT-qPCR. Microbiome DNA was extracted from stool samples and sequenced using an Ion PGM Torrent platform. Results: Synbiotic supplementation reduced body weight gain in the OT group compared with the OC group (p = 0.0398) and was associated with an increase in Enterobacteriaceae (p = 0.005) and a decrease in Cyanobacteria (p = 0.047), Clostridiaceae (p = 0.026), Turicibacterales (p = 0.005) and Coprococcus (p = 0.047). On the other hand, a significant reduction in Sutterella (p = 0.009) and Turicibacter (p = 0.005) bacteria was observed in the LT group compared to the LC group. Alpha and beta diversities were different among all treated groups. β-Catenin gene expression was significantly decreased in the gut tissue of the OT group (p ≤ 0.0001) compared to the other groups. No changes were observed in occludin, cadherin or zonulin gene expression in the gut tissue. Conclusions: Synbiotic supplementation prevents excessive weight gain, modulates the gut microbiota, and reduces β-catenin expression in ob/ob mice.

Downstream Signaling of Inflammasome Pathway Affects Patients' Outcome in the Context of Distinct Molecular Breast Cancer Subtypes

Inflammasomes are protein complexes involved in the regulation of different biological conditions. Over the past few years, the role of NLRP3 in different tumor types has gained interest. In breast cancer (BC), NLRP3 has been associated with multiple processes including epithelia mesenchymal transition, invasion and metastization. Little is known about molecular modifications of NLRP3 up-regulation. In this study, in a cohort of BCs, the expression levels of NLRP3 and PYCARD were analyzed in combination with CyclinD1 and MYC ones and their gene alterations. We described a correlation between the NLRP3/PYCARD axis and CyclinD1 (p < 0.0001). NLRP3, PYCARD and CyclinD1’s positive expression was observed in estrogen receptor (ER) and progesterone receptor (PgR) positive cases (p < 0.0001). Furthermore, a reduction of NLRP3 and PYCARD expression has been observed in triple negative breast cancers (TNBCs) with respect to the Luminal phenotypes (p = 0.017 and p = 0.0015, respectively). The association NLRP3+/CCND1+ or PYCARD+/CCND1+ was related to more aggressive clinicopathological characteristics and a worse clinical outcome, both for progression free survival (PFS) and overall survival (OS) with respect to NLRP3+/CCND1− or PYCARD+/CCND1− patients, both in the whole cohort and also in the subset of Luminal tumors. In conclusion, our study shows that the NLRP3 inflammasome complex is down-regulated in TNBC compared to the Luminal subgroup. Moreover, the expression levels of NLRP3 and PYCARD together with the alterations of CCND1 results in Luminal subtype BC’ss poor prognosis.

Wnt-Signaling Inhibitor Wnt-C59 Suppresses the Cytokine Upregulation in Multiple Organs of Lipopolysaccharide-Induced Endotoxemic Mice via Reducing the Interaction between β-Catenin and NF-κB

Sepsis is characterized by multiple-organ dysfunction caused by the dysregulated host response to infection. Until now, however, the role of the Wnt signaling has not been fully characterized in multiple organs during sepsis. This study assessed the suppressive effect of a Wnt signaling inhibitor, Wnt-C59, in the kidney, lung, and liver of lipopolysaccharide-induced endotoxemic mice, serving as an animal model of sepsis. We found that Wnt-C59 elevated the survival rate of these mice and decreased their plasma levels of proinflammatory cytokines and organ-damage biomarkers, such as BUN, ALT, and AST. The Wnt/β-catenin and NF-κB pathways were stimulated and proinflammatory cytokines were upregulated in the kidney, lung, and liver of endotoxemic mice. Wnt-C59, as a Wnt signaling inhibitor, inhibited the Wnt/β-catenin pathway, and its interaction with the NF-κB pathway, which resulted in the inhibition of NF-κB activity and proinflammatory cytokine expression. In multiple organs of endotoxemic mice, Wnt-C59 significantly reduced the β-catenin level and interaction with NF-κB. Our findings suggest that the anti-endotoxemic effect of Wnt-C59 is mediated via reducing the interaction between β-catenin and NF-κB, consequently suppressing the associated cytokine upregulation in multiple organs. Thus, Wnt-C59 may be useful for the suppression of the multiple-organ dysfunction during sepsis.

Targeting STAT3: A crucial modulator of sepsis

Signal transducer and activator of transcription 3 (STAT3) is a cellular signal transcription factor that has recently attracted a great deal of attention. It can trigger a variety of genes transcription in response to cytokines and growth factors stimulation, which plays an important role in many cellular biological processes involved in anti/proinflammatory responses. Sepsis is a life-threatening organ dysfunction resulting from dysregulated host responses to infection. As a converging point of multiple inflammatory responses pathways, accumulating studies have presented the elaborate network of STAT3 in sepsis pathophysiology; these results generally indicate a promising therapeutic application for targeting STAT3 in the treatment of sepsis. In the present review, we evaluated the published literature describing the use of STAT3 in the treatment of experimental and clinical sepsis. The information presented here may be useful for the design of future studies and may highlight the potential of STAT3 as a future biomarker and therapeutic target for sepsis.

LGK974 suppresses lipopolysaccharide-induced endotoxemia in mice by modulating the crosstalk between the Wnt/β-catenin and NF-κB pathways

Endotoxemia, a type of sepsis caused by gram-negative bacterial endotoxin [i.e., lipopolysaccharide (LPS)], is associated with manifestations such as cytokine storm; failure of multiple organs, including the liver; and a high mortality rate. We investigated the effect and mechanism of action of LGK974, a Wnt signaling inhibitor, in mice with LPS-induced endotoxemia, an animal model of sepsis. LGK974 significantly and dose-dependently increased the survival rate and reduced plasma cytokine levels in mice with LPS-induced endotoxemia. Transcriptome analysis of liver tissues revealed significant changes in the expression of genes associated with the Wnt pathway as well as cytokine and NF-κB signaling during endotoxemia. LGK974 treatment suppressed the activation of NF-κB signaling and cytokine expression as well as the Wnt/β-catenin pathway in the livers of endotoxemic mice. Coimmunoprecipitation of phospho-IκB and β-transducin repeat-containing protein (β-TrCP) was increased in the livers of endotoxemic mice but was reduced by LGK974 treatment. Moreover, LGK974 treatment decreased the coimmunoprecipitation and colocalization of β-catenin and NF-κB, which were elevated in the livers of endotoxemic mice. Our results reveal crosstalk between the Wnt/β-catenin and NF-κB pathways via interactions between β-TrCP and phospho-IκB and between β-catenin and NF-κB during endotoxemia. The results of this study strongly suggest that the crosstalk between the Wnt/β-catenin and NF-κB pathways contributes to the mutual activation of these two pathways during endotoxemia, which results in amplified cytokine production, liver damage and death, and that LGK974 suppresses this vicious amplification cycle by reducing the crosstalk between these two pathways.

Inflammation and Wnt Signaling: Target for Immunomodulatory Therapy?

Wnt proteins comprise a large family of highly conserved glycoproteins known for their role in development, cell fate specification, tissue regeneration, and tissue homeostasis. Aberrant Wnt signaling is linked to developmental defects, malignant transformation, and carcinogenesis as well as to inflammation. Mounting evidence from recent research suggests that a dysregulated activation of Wnt signaling is involved in the pathogenesis of chronic inflammatory diseases, such as neuroinflammation, cancer-mediated inflammation, and metabolic inflammatory diseases. Recent findings highlight the role of Wnt in the modulation of inflammatory cytokine production, such as NF-kB signaling and in innate defense mechanisms as well as in the bridging of innate and adaptive immunity. This sparked the development of novel therapeutic treatments against inflammatory diseases based on Wnt modulation. Here, we summarize the role and function of the Wnt pathway in inflammatory diseases and focus on Wnt signaling as underlying master regulator of inflammation that can be therapeutically targeted.

Increased H3K4me3 methylation and decreased miR-7113-5p expression lead to enhanced Wnt/β-catenin signaling in immune cells from PTSD patients leading to inflammatory phenotype

BACKGROUND

Posttraumatic stress disorder (PTSD) is a psychiatric disorder accompanied by chronic peripheral inflammation. What triggers inflammation in PTSD is currently unclear. In the present study, we identified potential defects in signaling pathways in peripheral blood mononuclear cells (PBMCs) from individuals with PTSD.

METHODS

RNAseq (5 samples each for controls and PTSD), ChIPseq (5 samples each) and miRNA array (6 samples each) were used in combination with bioinformatics tools to identify dysregulated genes in PBMCs. Real time qRT-PCR (24 samples each) and in vitro assays were employed to validate our primary findings and hypothesis.

RESULTS

By RNA-seq analysis of PBMCs, we found that Wnt signaling pathway was upregulated in PTSD when compared to normal controls. Specifically, we found increased expression of WNT10B in the PTSD group when compared to controls. Our findings were confirmed using NCBI's GEO database involving a larger sample size. Additionally, in vitro activation studies revealed that activated but not naïve PBMCs from control individuals expressed more IFNγ in the presence of recombinant WNT10B suggesting that Wnt signaling played a crucial role in exacerbating inflammation. Next, we investigated the mechanism of induction of WNT10B and found that increased expression of WNT10B may result from epigenetic modulation involving downregulation of hsa-miR-7113-5p which targeted WNT10B. Furthermore, we also observed that WNT10B overexpression was linked to higher expression of H3K4me3 histone modification around the promotor of WNT10B. Additionally, knockdown of histone demethylase specific to H3K4me3, using siRNA, led to increased expression of WNT10B providing conclusive evidence that H3K4me3 indeed controlled WNT10B expression.

CONCLUSIONS

In summary, our data demonstrate for the first time that Wnt signaling pathway is upregulated in PBMCs of PTSD patients resulting from epigenetic changes involving microRNA dysregulation and histone modifications, which in turn may promote the inflammatory phenotype in such cells.

Deletion of Nemo-like Kinase in T Cells Reduces Single-Positive CD8+ Thymocyte Population

The β-catenin/Wnt signaling pathway plays an important role in all stages of T cell development. Nemo-like kinase (NLK) is an evolutionary conserved serine/threonine kinase and a negative regulator of the Wnt signaling pathway. NLK can directly phosphorylate histone deacetylase 1 (HDAC1), as well as T cell factor/lymphoid enhancer-binding factor (TCF/LEF), causing subsequent repression of target gene transcription. By engineering mice lacking NLK in early stages of T cell development, we set out to characterize the role NLK plays in T cell development and found that deletion of NLK does not affect mouse health or lymphoid tissue development. Instead, these mice harbored a reduced number of single-positive (SP) CD8⁺ thymocytes without any defects in the SP CD4⁺ thymocyte population. The decrease in SP CD8⁺ thymocytes was not caused by a block in differentiation from double-positive CD4⁺CD8⁺ cells. Neither TCR signaling nor activation was altered in the absence of NLK. Instead, we observed a significant increase in cell death and reduced phosphorylation of LEF1 as well as HDAC1 among NLK-deleted SP CD8⁺ cells. Thus, NLK seems to play an important role in the survival of CD8⁺ thymocytes. Our data provide evidence for a new function for NLK with regard to its involvement in T cell development and supporting survival of SP CD8⁺ thymocytes.

β-catenin promotes NLRP3 inflammasome activation via increasing the association between NLRP3 and ASC

NLRP3 (NOD-, LRR- and pyrin domain- containing protein 3) inflammasome is involved in diverse inflammatory diseases, so the activation of NLRP3 inflammasome needs to be tightly regulated to prevent excessive inflammation. However, the endogenous regulatory mechanisms of NLRP3 inflammasome are still less defined. Here, we report that β-catenin, which is the central mediator of the canonical Wnt/β-catenin signaling, promotes NLRP3 inflammasome activation. When we suppressed the expression of β-catenin by siRNA or pharmacological inhibitor, the NLRP3 inflammasome activation was impaired. Accordingly, β-catenin inhibitor attenuated LPS-induced systemic inflammation in vivo. Mechanistically, we found β-catenin interacted with NLRP3 and promoted the association between NLRP3 and ASC. Thus, our study revealed a novel role of β-catenin in NLRP3 inflammasome activation and suggest an endogenous crosstalk between Wnt/β-catenin signal and NLRP3 inflammasome.

Suppressive Effects of GSS on Lipopolysaccharide-Induced Endothelial Cell Injury and ALI via TNF-α and IL-6

Background. Under septic conditions, LPS induced lung vascular endothelial cell (EC) injury, and the release of inflammatory mediator launches and aggravates acute lung injury (ALI). There are no effective therapeutic options for ALI. Genistein-3'-sodium sulfonate (GSS) is a derivative of native soy isoflavone, which exhibits neuroprotective effects via its antiapoptosis property. However, whether GSS protect against sepsis-induced EC injury and release of inflammatory mediators has not been determined. In this study, we found that GSS not only downregulated the levels of TNF-α and IL-6 in the lung and serum of mice in vivo but also inhibited the expression and secretion of TNF-α and IL-6 in ECs. Importantly, we also found that GSS blocked LPS-induced TNF-α and IL-6 expression in ECs via the Myd88/NF-κB signaling pathway. Taken together, our results demonstrated that GSS might be a promising candidate for sepsis-induced ALI via its regulating effects on inflammatory response in lung ECs.

Functions of the WNT Signaling Network in Shaping Host Responses to Infection

It is well-established that aberrant WNT expression and signaling is associated with developmental defects, malignant transformation and carcinogenesis. More recently, WNT ligands have emerged as integral components of host responses to infection but their functions in the context of immune responses are incompletely understood. Roles in the modulation of inflammatory cytokine production, host cell intrinsic innate defense mechanisms, as well as the bridging of innate and adaptive immunity have been described. To what degree WNT responses are defined by the nature of the invading pathogen or are specific for subsets of host cells is currently not well-understood. Here we provide an overview of WNT responses during infection with phylogenetically diverse pathogens and highlight functions of WNT ligands in the host defense against infection. Detailed understanding of how the WNT network orchestrates immune cell functions will not only improve our understanding of the fundamental principles underlying complex immune response, but also help identify therapeutic opportunities or potential risks associated with the pharmacological targeting of the WNT network, as currently pursued for novel therapeutics in cancer and bone disorders.

Inflammatory cytokines and organ dysfunction associate with the aberrant DNA methylome of monocytes in sepsis

BACKGROUND

Sepsis, a life-threatening organ dysfunction caused by a dysregulated systemic immune response to infection, associates with reduced responsiveness to subsequent infections. How such tolerance is acquired is not well understood but is known to involve epigenetic and transcriptional dysregulation.

METHODS

Bead arrays were used to compare global DNA methylation changes in patients with sepsis, non-infectious systemic inflammatory response syndrome, and healthy controls. Bioinformatic analyses were performed to dissect functional reprogramming and signaling pathways related to the acquisition of these specific DNA methylation alterations. Finally, in vitro experiments using human monocytes were performed to test the induction of similar DNA methylation reprogramming.

RESULTS

Here, we focused on DNA methylation changes associated with sepsis, given their potential role in stabilizing altered phenotypes. Tolerized monocytes from patients with sepsis display changes in their DNA methylomes with respect to those from healthy controls, affecting critical monocyte-related genes. DNA methylation profiles correlate with IL-10 and IL-6 levels, significantly increased in monocytes in sepsis, as well as with the Sequential Organ Failure Assessment score; the observed changes associate with TFs and pathways downstream to toll-like receptors and inflammatory cytokines. In fact, in vitro stimulation of toll-like receptors in monocytes results in similar gains and losses of methylation together with the acquisition of tolerance.

CONCLUSION

We have identified a DNA methylation signature associated with sepsis that is downstream to the response of monocytes to inflammatory signals associated with the acquisition of a tolerized phenotype and organic dysfunction.

The role of Wnt signaling in the healing myocardium: a focus on cell specificity

Various cell types are involved in the healing process after myocardial infarction (MI). Besides cardiac resident cells (such as cardiomyocytes, fibroblasts and endothelial cells) already present at the lesion site, a massive influx of leukocytes (mainly monocytes and neutrophils) is observed within hours after the ischemic event. So far, little is known about modes of interaction of these cells. Wnt signaling is an evolutionary conserved signaling cassette known to play an important role in cell-cell communication. While the overall reactivation of Wnt signaling upon ischemic injury is well described, the precise expression pattern of Wnt proteins, however, is far from understood. We here describe known Wnt components that partake in MI healing and differentiate cell-specific aspects. The secretion of Wnt proteins and their antagonists in the context of cardiac inflammation after MI appear to be tightly regulated in a spatial-temporal manner. Overall, we aim to stress the importance of elucidating not only Wnt component-specific aspects, but also their sometimes contradicting effects in different target cells. A better understanding of Wnt signaling in MI healing may eventually lead to the development of successful therapeutic approaches in an often considered "un-druggable" pathway.