Sepsis Upregulates CD14 Expression in a MyD88-Dependent and Trif-Independent Pathway

IRF3 function and immunological gaps in sepsis

Lipopolysaccharide (LPS) induces potent cell activation via Toll-like receptor 4/myeloid differentiation protein 2 (TLR4/MD-2), often leading to septic death and cytokine storm. TLR4 signaling is diverted to the classical acute innate immune, inflammation-driving pathway in conjunction with the classical NF-κB pivot of MyD88, leading to epigenetic linkage shifts in nuclear pro-inflammatory transcription and chromatin structure-function; in addition, TLR4 signaling to the TIR domain-containing adapter-induced IFN-β (TRIF) apparatus and to nuclear pivots that signal the association of interferons alpha and beta (IFN-α and IFN-β) with acute inflammation, often coupled with oxidants favor inhibition or resistance to tissue injury. Although the immune response to LPS, which causes sepsis, has been clarified in this manner, there are still many current gaps in sepsis immunology to reduce mortality. Recently, selective agonists and inhibitors of LPS signals have been reported, and there are scattered reports on LPS tolerance and control of sepsis development. In particular, IRF3 signaling has been reported to be involved not only in sepsis but also in increased pathogen clearance associated with changes in the gut microbiota. Here, we summarize the LPS recognition system, main findings related to the IRF3, and finally immunological gaps in sepsis.

Interpreting biologically informed neural networks for enhanced proteomic biomarker discovery and pathway analysis

The incorporation of machine learning methods into proteomics workflows improves the identification of disease-relevant biomarkers and biological pathways. However, machine learning models, such as deep neural networks, typically suffer from lack of interpretability. Here, we present a deep learning approach to combine biological pathway analysis and biomarker identification to increase the interpretability of proteomics experiments. Our approach integrates a priori knowledge of the relationships between proteins and biological pathways and biological processes into sparse neural networks to create biologically informed neural networks. We employ these networks to differentiate between clinical subphenotypes of septic acute kidney injury and COVID-19, as well as acute respiratory distress syndrome of different aetiologies. To gain biological insight into the complex syndromes, we utilize feature attribution-methods to introspect the networks for the identification of proteins and pathways important for distinguishing between subtypes. The algorithms are implemented in a freely available open source Python-package ( https://github.com/InfectionMedicineProteomics/BINN ).

The kinetics of signaling through the common FcRγ chain determine cytokine profiles in dendritic cells

The common Fc receptor γ (FcRγ) chain is a signaling subunit common to several immune receptors, but cellular responses induced by FcRγ-coupled receptors are diverse. We investigated the mechanisms by which FcRγ generates divergent signals when coupled to Dectin-2 and Mincle, structurally similar C-type lectin receptors that induce the release of different cytokines from dendritic cells. Chronological tracing of transcriptomic and epigenetic changes upon stimulation revealed that Dectin-2 induced early and strong signaling, whereas Mincle-mediated signaling was delayed, which reflects their expression patterns. Generation of early and strong FcRγ-Syk signaling by engineered chimeric receptors was sufficient to recapitulate a Dectin-2-like gene expression profile. Early Syk signaling selectively stimulated the activity of the calcium ion-activated transcription factor NFAT, which rapidly altered the chromatin status and transcription of the Il2 gene. In contrast, proinflammatory cytokines, such as TNF, were induced regardless of FcRγ signaling kinetics. These results suggest that the strength and timing of FcRγ-Syk signaling can alter the quality of cellular responses through kinetics-sensing signaling machineries.

CASP-Model Sepsis Triggers Systemic Innate Immune Responses Revealed by the Systems-Level Signaling Pathways

Colon ascendens stent peritonitis (CASP) surgery induces a leakage of intestinal contents which may cause polymicrobial sepsis related to post-operative failure of remote multi-organs (including kidney, liver, lung and heart) and possible death from systemic syndromes. Mechanisms underlying such phenomena remain unclear. This article aims to elucidate the mechanisms underlying the CASP-model sepsis by analyzing real-world GEO data (GSE24327_A, B and C) generated from mice spleen 12 hours after a CASP-surgery in septic MyD88-deficient and wildtype mice, compared with untreated wildtype mice. Firstly, we identify and characterize 21 KO MyD88-associated signaling pathways, on which true key regulators (including ligands, receptors, adaptors, transducers, transcriptional factors and cytokines) are marked, which were coordinately, significantly, and differentially expressed at the systems-level, thus providing massive potential biomarkers that warrant experimental validations in the future. Secondly, we observe the full range of polymicrobial (viral, bacterial, and parasitic) sepsis triggered by the CASP-surgery by comparing the coordinated up- or down-regulations of true regulators among the experimental treatments born by the three data under study. Finally, we discuss the observed phenomena of “systemic syndrome”, “cytokine storm” and “KO MyD88 attenuation”, as well as the proposed hypothesis of “spleen-mediated immune-cell infiltration”. Together, our results provide novel insights into a better understanding of innate immune responses triggered by the CASP-model sepsis in both wildtype and MyD88-deficient mice at the systems-level in a broader vision. This may serve as a model for humans and ultimately guide formulating the research paradigms and composite strategies for the early diagnosis and prevention of sepsis.

Presepsin production in monocyte/macrophage-mediated phagocytosis of neutrophil extracellular traps

Presepsin, a biomarker discovered in Japan, has been clinically applied as a diagnostic aid for sepsis. Recently, however, it has been reported that presepsin levels are elevated in patients with severe systemic lupus erythematosus without infection, suggesting the existence of a production mechanism that does not involve bacterial phagocytosis. In this study, we aimed to elucidate the mechanism of presepsin production without bacterial phagocytosis and explore the clinical significance of presepsin. Neutrophil extracellular traps (NETs) were induced by Escherichia coli and phorbol myristate acetate (PMA) in neutrophils isolated from the peripheral blood of healthy subjects. NET induction alone did not increase presepsin levels, but co-culturing with monocytes significantly increased them. The addition of a NET formation inhibitor also suppressed presepsin levels, suggesting that presepsin production is greatly influenced by monocyte phagocytosis of NETs. Phagocytosis of NETs by THP-1 and U937 cells, which was induced by CD14 expression, also increased presepsin levels. This study suggests that presepsin can be used to assess the severity of inflammatory diseases, such as autoimmune diseases, and monitor treatment effects.

The Role of Innate Immunity in Natural Elite Controllers of HIV-1 Infection

The natural process of human immunodeficiency virus type 1(HIV-1) infection is characterized by high viral load, immune cell exhaustion, and immunodeficiency, which eventually leads to the stage of acquired immunodeficiency syndrome (AIDS) and opportunistic infections. Rapidly progressing HIV-1 individuals often die of AIDS several years after infection without treatment. The promotion of ART greatly prolongs the survival time of HIV-infected persons. However, some patients have incomplete immune function reconstruction after ART due to latent storage of HIV-infected cells. Therefore, how to achieve a functional cure has always been the focus and hot spot of global AIDS research. Fortunately, the emergence of ECs/LTNPs who can control virus replication naturally has ignited new hope for realizing a functional cure for AIDS. Recently, a special category of infected individuals has attracted attention that can delay the progression of the disease more rigorously than the natural progression of HIV-1 infection described above. These patients are characterized by years of HIV-1 infection, long-term asymptomatic status, and normal CD4+T cell count without ART, classified as HIV-infected long-term nonprogressors (LTNPs) and elite controllers (ECs). Numerous studies have shown that the host and virus jointly determine the progression of HIV-1 infection, in which the level of innate immunity activation plays an important role. As the first line of defense against pathogen invasion, innate immunity is also a bridge to induce adaptive immunity. Compared with natural progressors, innate immunity plays an antiviral role in HIV-1 infection by inducing or activating many innate immune-related factors in the natural ECs. Learning the regulation of ECs immunity, especially the innate immunity in different characteristics, and thus studying the mechanism of the control of disease progression naturally, will contribute to the realization of the functional cure of AIDS. Therefore, this review will explore the relationship between innate immunity and disease progression in ECs of HIV-1 infection from the aspects of innate immune cells, signaling pathways, cytokines, which is helpful to provide new targets and theoretical references for the functional cure, prevention and control of AIDS, and development of a vaccine.

Liver and Kidney Surgical Anatomy to Verify the Effect of miR-221 on Organ Damage in Septic Rats

Background

Related studies have shown that miR-221 has the ability to promote inflammatory response. This experiment mainly discusses the effect of miR-221 on acute liver and kidney injury in septic rats.

Method

Thirty Sprague Dawley (SD) rats were randomly divided into a (1) control group, (2) sepsis group, (3) miR-221 overexpression group, (4) miR-221 inhibition group, (5) HECTD2 inhibition group, and (6) miR-221 overexpression + HECTD2 inhibition group. The sepsis rat model was prepared by cecal ligation and puncture (CLP). The expression levels of miR-221 and HECTD2 were detected by RT-qPCR. The levels of aspartate aminotransferase (AST) and alanine aminotransferase (ALT) in the liver were detected by the IFCC method. The levels of blood urea nitrogen (BUN) were detected by the creatine oxidase method. The levels of inflammatory factors were detected by ELISA. The apoptosis rate of liver and kidney cells was detected by flow cytometry. The expression of p65 protein was detected by western blotting.

Result

RT-qPCR results showed that the expressions of miR-221 and HECTD2 were upregulated in septic rats (P < 0.05). Compared with group 1, the liver function index, kidney function index, liver and kidney apoptosis rate, serum inflammatory factor level, and p65 protein expression in each group were increased (P < 0.05). Compared with group 2, the liver function index, kidney function index, liver and kidney apoptosis rate, serum inflammatory factor level, and p65 protein expression in groups 4 and 5 were decreased (P < 0.05). Compared with group 2, the expression of HECTD2 was upregulated in group 3 (P < 0.05). Compared with group 3, the liver function index, renal function index, liver and kidney apoptosis rate, serum inflammatory factor level, and p65 protein expression were decreased in group 6 (P < 0.05).

Conclusion

MiR-221 promotes the expression of HECTD2 in septic rats, and inhibition of miR-221 expression can reduce the degree of liver and kidney injury in septic rats.

Anti-inflammatory effect of Barringtonia angusta methanol extract is mediated by targeting of Src in the NF-κB signalling pathway

CONTEXT

Among the plants in the genus Barringtonia (Lecythidaceae) used as traditional medicines to treat arthralgia, chest pain, and haemorrhoids in Indonesia, Barringtonia racemosa L. and Barringtonia acutangula (L.) Gaertn. have demonstrated anti-inflammatory activity in systemic inflammatory models.

OBJECTIVE

The anti-inflammatory activity of Barringtonia angusta Kurz has not been investigated. We prepared a methanol extract of the leaves and stems of B. angusta (Ba-ME) and systemically evaluated its anti-inflammatory effects in vitro and in vivo.

MATERIALS AND METHODS

RAW264.7 cells stimulated with LPS or Pam3CSK4 for 24 h were treated with Ba-ME (12.5, 25, 50, 100, and 150 µg/mL), and NO production and mRNA levels of inflammatory genes were evaluated. Luciferase reporter gene assay, western blot analysis, overexpression experiments, and cellular thermal shift assay were conducted to explore the mechanism of Ba-ME. In addition, the anti-gastritis activity of Ba-ME (50 and 100 mg/kg, administered twice per day for two days) was evaluated using an HCl/EtOH-induced gastritis mouse model.

RESULTS

Ba-ME dose-dependently suppressed NO production [IC₅₀ = 123.33 µg/mL (LPS) and 46.89 µg/mL (Pam3CSK4)] without affecting cell viability. Transcriptional expression of iNOS, IL-1β, COX-2, IL-6, and TNF-α and phosphorylation of Src, IκBα, p50/105, and p65 were inhibited by Ba-ME. The extract specifically targeted the Src protein by binding to its SH2 domain. Moreover, Ba-ME significantly ameliorated inflammatory lesions in the HCl/EtOH-induced gastritis model.

DISCUSSION AND CONCLUSIONS

The anti-inflammatory activity of Ba-ME is mediated by targeting of the Src/NF-κB signalling pathway, and B. angusta has potential as an anti-inflammatory drug.

Integrin β3 Modulates TLR4-Mediated Inflammation by Regulation of CD14 Expression in Macrophages in Septic Condition

Sepsis is a major challenge in clinical practice and responsible for high mortality. Recent studies indicated that integrins participated in toll-like-receptor (TLR)-mediated innate immunity. In the present study, we investigated the mechanism of integrin β3 and TLR4 signaling using a cecal ligation and puncture (CLP)-induced sepsis and lipopolysaccharide (LPS)-treated macrophage cell model. In a lethal CLP model, the survival rate of integrin β3 mice was higher than that of wild-type mice. The levels of alanine aminotransferase, aspartate transaminase, creatinine, blood urea nitrogen , and lactate dehydrogenase in the serum and cluster of differentiation 14 (CD14) protein expression in the tissues were significantly decreased in integrin β3 mice. A similar effect with regard to CD14 down-regulation was observed in septic TLR4 mice. In wild-type macrophages, the inhibition of integrin β3 by P11 or with a specific antibody, inhibited TNF-α, and IL-6 release at the early time period of LPS stimulation. However, during the late periods of LPS stimulation this effect was not noted. CD14 expression levels had no change in such treatment. In contract, LPS-induced TNF-α and IL-6 release and LPS-induced CD14 expression were significantly decreased in integrin β3macrophages. The inhibition of the TLR4 pathway by TAK-242, or in TLR4 mutant macrophages abolished LPS-induced CD14 expression. Integrin β3 pathway activation by vitronectin exhibited no effect in CD14 expression. Furthermore, recombinant CD14 protein stimulation reversed integrin β3 deficiency and caused lower TNF-α and IL-6 release. Moreover, the molecular interaction of TLR4 and integrin β3 was significantly increased following LPS stimulation. In conclusion, integrin β3 positively regulated TLR4-mediated inflammatory responses via CD14 expression in macrophages in septic condition. Specifically targeting integrin β3/TLR4-CD14 signaling pathway may be a potential treatment strategy for polymicrobial sepsis.

Olaparib attenuates sepsis-induced acute multiple organ injury via ERK-mediated CD14 expression

Sepsis is characterized by persistent systemic inflammation, which can cause multi-organ dysfunction. The poly polymerase-1 inhibitor olaparib possesses anti-inflammatory properties. This study aimed to assess the effects of olaparib (pre- and post-treatments) on sepsis, and to investigate whether it could suppress CD14 expression via the ERK pathway in polymicrobial sepsis and peritoneal macrophages models. Sepsis was induced by cecal ligation and puncture in C57BL/6 male mice. Fifty mice were randomly divided into five groups: The sham group was treated with vehicle or olaparib, the cecal ligation and puncture group with vehicle or with olaparib (5 mg/kg i.p.) 1 h before or 2 h after surgery. Olaparib pretreatment significantly improved the survival of septic mice (P < 0.001). Pre- and post-treatment of mice with olaparib partly alleviated cecal ligation and puncture-induced organ injury by decreasing the amounts of the pro-inflammatory mediators TNF-α and IL-6 as well as bacterial burden in the serum, peritoneal lavage fluid, and organs (P < 0.05). The protective effect of olaparib was associated with CD14 suppression via inhibition of ERK activation. Olaparib facilitated negative regulation of ERK-mediated CD14 expression, which may contribute to multi-organ injury in sepsis.

Advanced glycation end-products reduce lipopolysaccharide uptake by macrophages

Hyperglycaemia provides a suitable environment for infections and the mechanisms of glucose toxicity include the formation of advanced glycation end-products (AGEs), which comprise non-enzymatically glycosylated proteins, lipids, and nucleic acid amino groups. Among AGE-associated phenotypes, glycolaldehyde-derived toxic AGE (AGE-3) is involved in the pathogenesis of diabetic complications. Internalisation of endotoxin by various cell types contributes to innate immune responses against bacterial infection. An endotoxin derived from Gram-negative bacteria, lipopolysaccharide (LPS), was reported to enhance its own uptake by RAW264.7 mouse macrophage-like cells, and an LPS binding protein, CD14, was involved in the LPS uptake. The LPS uptake induced the activation of RAW264.7 leading to the production of chemokine CXC motif ligand (CXCL) 10, which promotes T helper cell type 1 responses. Previously, we reported that AGE-3 was internalised into RAW264.7 cells through scavenger receptor-1 Class A. We hypothesized that AGEs uptake interrupt LPS uptake and impair innate immune response to LPS in RAW264.7 cells. In the present study, we found that AGE-3 attenuated CD14 expression, LPS uptake, and CXCL10 production, which was concentration-dependent, whereas LPS did not affect AGE uptake. AGEs were reported to stimulate the receptor for AGEs and Toll-like receptor 4, which cause inflammatory reactions. We found that inhibitors for RAGE, but not Toll-like receptor 4, restored the AGE-induced suppression of CD14 expression, LPS uptake, and CXCL10 production. These results indicate that the receptor for the AGE-initiated pathway partially impairs the immune response in diabetes patients.

Tropomodulin1 Expression Increases Upon Maturation in Dendritic Cells and Promotes Their Maturation and Immune Functions

Dendritic cells (DCs) are the most potent antigen-presenting cells. Upon maturation, DCs express costimulatory molecules and migrate to the lymph nodes to present antigens to T cells. The actin cytoskeleton plays key roles in multiple aspects of DC functions. However, little is known about the mechanisms and identities of actin-binding proteins that control DC maturation and maturation-associated functional changes. Tropomodulin1 (Tmod1), an actin-capping protein, controls actin depolymerization and nucleation. We found that Tmod1 was expressed in bone marrow-derived immature DCs and was significantly upregulated upon lipopolysaccharide (LPS)-induced DC maturation. By characterizing LPS-induced mature DCs (mDCs) from Tmod1 knockout mice, we found that compared with Tmod1+/+ mDCs, Tmod1-deficient mDCs exhibited lower surface expression of costimulatory molecules and chemokine receptors and reduced secretion of inflammatory cytokines, suggesting that Tmod1 deficiency retarded DC maturation. Tmod1-deficient mDCs also showed impaired random and chemotactic migration, deteriorated T-cell stimulatory ability, and reduced F-actin content and cell stiffness. Furthermore, Tmod1-deficient mDCs secreted high levels of IFN-β and IL-10 and induced immune tolerance in an experimental autoimmune encephalomyelitis (EAE) mouse model. Mechanistically, Tmod1 deficiency affected TLR4 signaling transduction, resulting in the decreased activity of MyD88-dependent NFκB and MAPK pathways but the increased activity of the TRIF/IRF3 pathway. Rescue with exogenous Tmod1 reversed the effect of Tmod1 deficiency on TLR4 signaling. Therefore, Tmod1 is critical in regulating DC maturation and immune functions by regulating TLR4 signaling and the actin cytoskeleton. Tmod1 may be a potential target for modulating DC functions, a strategy that would be beneficial for immunotherapy for several diseases.

Data-Independent Acquisition-Based Quantitative Proteomics Analysis Reveals Dynamic Network Profiles during the Macrophage Inflammatory Response

Understanding of the molecular regulatory mechanisms underlying the inflammatory response is incomplete. The present study focuses on characterizing the proteome in a model of inflammation in macrophages treated with lipopolysaccharide (LPS). A total of 3597 proteins are identified in macrophages with the data-independent acquisition (DIA) method. Bioinformatic analyses reveal discrete modules and the underlying molecular mechanisms, as well as the signaling network that modulates the development of inflammation. It is found that a total of 87 differentially expressed proteins are shared by all stages of LPS-induced inflammation in macrophages and that 18 of these proteins participate in metabolic processes by forming a tight interaction network. Data support the hypothesis that ribosome proteins play a key role in regulating the macrophage response to LPS. Interestingly, conjoint analyses of the transcriptome and proteome in macrophages treated with LPS reveal that the genes upregulated at both the mRNA and protein levels are mainly involved in inflammation and the immune response, whereas the genes downregulated are significantly enriched in metabolism-related processes. These results not only provide a more comprehensive understanding of the molecular mechanisms of inflammation mediated by bacterial infection but also provide a dynamic proteomic resource for further studies.

Resveratrol Downregulates Biomarkers of Sepsis Via Inhibition of Proteasome's Proteases

Lipopolysaccharide (LPS) is the main agonist of gram-negative bacteria and initiates inflammation. We recently reported that plasmas from sepsis patients revealed increased levels of following group of biomarkers; VCAM-1, ICAM1, CRP, resistin, and proteasome LMP subunits. Our objective here was to compare effects of resveratrol (shown to be a nonspecific proteasome inhibitor by us) and a known LMP7 inhibitor (ONX-0914, specific inhibitor) on proteasome's activities, as well as on inflammatory markers mentioned above in human blood monocytes. Using fluorescence-based assays on blood monocytes purified proteasomes, resveratrol (0-100 μM) inhibited all three protease activities, predominantly LMP7. Similarly, resveratrol inhibited all three protease activities using cell-based luminescence assay. In contrast, ONX-0914 was more selective and potent for LMP7 activity. Resveratrol and ONX-0914, both significantly inhibited expression of LPS-induced biomarkers mentioned above in CD14 monocytes. Moreover, resveratrol itself, as well as in combination with LPS, accumulated pIκBα in CD14 monocytes. Collectively, our data suggest that resveratrol is a less potent inhibitor of all three; CT-like (predominantly LMP7), T-like and PA protease activities and is less toxic to human monocytes than ONX-0914 (a selector inhibitor of only LMP7) as observed by an autophagy detection kit. Also, resveratrol reduces LPS-induced inflammatory cytokine expression by decreasing the translocation of NF-κB due to an increase in inhibitor pIκBα. Therefore, resveratrol can be used to curb inflammation in diseased states like sepsis and other disorders.

Toll-like receptors in the functional orientation of cardiac progenitor cells

Cardiac progenitor cells (CPCs) have the potential to differentiate into several cell lineages with the ability to restore in cardiac tissue. Multipotency and self-renewal activity are the crucial characteristics of CPCs. Also, CPCs have promising therapeutic roles in cardiac diseases such as valvular disease, thrombosis, atherosclerosis, congestive heart failure, and cardiac remodeling. Toll-like receptors (TLRs), as the main part of the innate immunity, have a key role in the development and differentiation of immune cells. Some reports are found regarding the effect of TLRs in the maturation of stem cells. This article tried to find the potential role of TLRs in the dynamics of CPCs. By showing possible crosstalk between the TLR signaling pathways and CPCs dynamics, we could achieve a better conception related to TLRs in the regeneration of cardiac tissue.

Magnesium sulfate inhibits binding of lipopolysaccharide to THP-1 cells by reducing expression of cluster of differentiation 14

We investigated effects of magnesium sulfate (MgSO₄) on modulating lipopolysaccharide (LPS)-macrophage binding and cluster of differentiation 14 (CD14) expression. Flow cytometry data revealed that the mean levels of LPS-macrophage binding and membrane-bound CD14 expression (mCD14) in differentiated THP-1 cells (a human monocytic cell line) treated with LPS plus MgSO₄ (the LPS + M group) decreased by 28.2% and 25.3% compared with those THP-1 cells treated with LPS only (the LPS group) (P < 0.001 and P = 0.037), indicating that MgSO₄ significantly inhibits LPS-macrophage binding and mCD14 expression. Notably, these effects of MgSO₄ were counteracted by L-type calcium channel activation. Moreover, the mean level of soluble CD14 (sCD14; proteolytic cleavage product of CD14) in the LPS + M group was 25.6% higher than in the LPS group (P < 0.001), indicating that MgSO₄ significantly enhances CD14 proteolytic cleavage. Of note, serine protease inhibition mitigated effects of MgSO₄ on both decreasing mCD14 and increasing sCD14. In conclusion, MgSO₄ inhibits LPS-macrophage binding through reducing CD14 expression. The mechanisms may involve antagonizing L-type calcium channels and activating serine proteases.