Suppression of inflammation in rat autoimmune myocarditis by S100A8/A9 through modulation of the proinflammatory cytokine network

Single cell RNA sequencing reveals immunomodulatory effects of stem cell factor and granulocyte colony-stimulating factor treatment in the brains of aged APP/PS1 mice

Alzheimers disease leads to progressive neurodegeneration and dementia. Alzheimers disease primarily affects older adults with neuropathological changes including amyloid beta deposition, neuroinflammation, and neurodegeneration. We have previously demonstrated that systemic treatment with combined stem cell factor, SCF, and granulocyte colony stimulating factor, GCSF, reduces amyloid beta load, increases amyloid beta uptake by activated microglia and macrophages, reduces neuroinflammation, and restores dendrites and synapses in the brains of aged APP-PS1 mice. However, the mechanisms underlying SCF-GCSF-enhanced brain repair in aged APP-PS1 mice remain unclear. This study used a transcriptomic approach to identify potential mechanisms by which SCF-GCSF treatment modulates microglia and peripheral myeloid cells to mitigate Alzheimers disease pathology in the aged brain. After injections of SCF-GCSF for 5 consecutive days, single cell RNA sequencing was performed on CD11b positive cells isolated from the brains of 28-month-old APP-PS1 mice. The vast majority of cell clusters aligned with transcriptional profiles of microglia in various activation states. However, SCF-GCSF treatment dramatically increased a cell population showing upregulation of marker genes related to peripheral myeloid cells. Flow cytometry data also revealed an SCF-GCSF-induced increase of cerebral CD45high-CD11b positive active phagocytes. SCF-GCSF treatment robustly increased the transcription of genes implicated in immune cell activation, including gene sets that regulate inflammatory processes and cell migration. Expression of S100a8 and S100a9 were robustly enhanced following SCF-GCSF treatment in all CD11b positive cell clusters. Moreover, the topmost genes differentially expressed with SCF-GCSF treatment were largely upregulated in S100a8-S100a9 positive cells, suggesting a well-conserved transcriptional profile related to SCF-GCSF treatment in resident and peripherally derived CD11b positive immune cells. This S100a8-S100a9-associated transcriptional profile contained notable genes related to proinflammatory and antiinflammatory responses, neuroprotection, and amyloid beta plaque inhibition or clearance. Altogether, this study reveals immunomodulatory effects of SCF-GCSF treatment in the aged brain with Alzheimers disease pathology, which will guide future studies to further uncover the therapeutic mechanisms.

Sodium dichloroacetate improves migration ability by suppressing LPS-induced inflammation in HTR-8/SVneo cells via the TLR4/NF-κB pathway

Objectives

Inadequate cytotrophoblast migration and invasion are speculated to result in preeclampsia, which is a pro-inflammatory condition. Sodium dichloroacetate (DCA) exerts anti-inflammatory actions. Thus,we sought to investigate the effect of DCA on the migration function of the lipopolysaccharide (LPS)-stimulated human-trophoblast-derived cell line (HTR-8/SVneo).

Materials and Methods

HTR-8/SVneo cells were treated with LPS to suppress cell migration. Cell migration was examined by both scratch wound healing assay and transwell migration assay. Western blotting was used to analyze the expression levels of toll-like receptor-4 (TLR4), nuclear factor-κB (NF-κB), TNF-α, IL-1β, and IL-6 in the cells.

Results

DCA reversed LPS-induced inhibition of migration in HTR-8/SVneo cells. Furthermore, DCA significantly suppressed LPS-induced activation of TLR4, phosphorylation of NF-κB (p65), translocation of p65 into the nucleus, and the production of pro-inflammatory cytokines (TNF-α, IL-1β, and IL-6). Treatment with inhibitors of TLR4 signal transduction (CLI095 or MD2-TLR-4-IN-1) reduced LPS-induced overexpression of pro-inflammatory cytokines, and a synergistic effect was found between TLR4 inhibitors and DCA in HTR-8/SVneo cells.

Conclusion

DCA improved trophoblast cell migration function by suppressing LPS-induced inflammation, at least in part, via the TLR4/NF-κB signaling pathway. This result indicates that DCA might be a potential therapeutic candidate for human pregnancy-related complications associated with trophoblast disorder.

S100 proteins in cardiovascular diseases

Cardiovascular diseases have become a serious threat to human health and life worldwide and have the highest fatality rate. Therefore, the prevention and treatment of cardiovascular diseases have become a focus for public health experts. The expression of S100 proteins is cell- and tissue-specific; they are implicated in cardiovascular, neurodegenerative, and inflammatory diseases and cancer. This review article discusses the progress in the research on the role of S100 protein family members in cardiovascular diseases. Understanding the mechanisms by which these proteins exert their biological function may provide novel concepts for preventing, treating, and predicting cardiovascular diseases.

Pathogenic roles of neutrophil-derived alarmins (S100A8/A9) in heart failure: From molecular mechanisms to therapeutic insights

An excessive neutrophil count is recognized as a valuable predictor of inflammation and is associated with a higher risk of adverse cardiac events in patients with heart failure. Our understanding of the effectors used by neutrophils to inflict proinflammatory actions needs to be advanced. Recently, emerging evidence has demonstrated a causative role of neutrophil-derived alarmins (i.e. S100A8/A9) in aggravating cardiac injuries by induction of inflammation. In parallel with the neutrophil count, high circulating levels of S100A8/A9 proteins powerfully predict mortality in patients with heart failure. As such, a deeper understanding of the biological functions of neutrophil-derived S100A8/A9 proteins would offer novel therapeutic insights. Here, the basic biology of S100A8/A9 proteins and their pleiotropic roles in cardiovascular diseases are discussed, focusing on heart failure. We also consider the evidence that therapeutic targeting of S100A8/A9 proteins by the humanized vaccine, antibodies or inhibitors is able to town down inflammatory injuries.

Novel mechanisms of thrombo-inflammation during infection: spotlight on neutrophil extracellular trap-mediated platelet activation

A state-of-the-art lecture titled "novel mechanisms of thrombo-inflammation during infection" was presented at the ISTH Congress in 2022. Platelet, neutrophil, and endothelial cell activation coordinate the development, progression, and resolution of thrombo-inflammatory events during infection. Activated platelets and neutrophil extracellular traps (NETs) are frequently observed in patients with sepsis and COVID-19, and high levels of NET-derived damage-associated molecular patterns (DAMPs) correlate with thrombotic complications. NET-associated DAMPs induce direct and indirect platelet activation, which in return potentiates neutrophil activation and NET formation. These coordinated interactions involve multiple receptors and signaling pathways contributing to vascular and organ damage exacerbating disease severity. This state-of-the-art review describes the main mechanisms by which platelets support NETosis and the key mechanisms by which NET-derived DAMPs trigger platelet activation and the formation of procoagulant platelets leading to thrombosis. We report how these DAMPs act through multiple receptors and signaling pathways differentially regulating cell activation and disease outcome, focusing on histones and S100A8/A9 and their contribution to the pathogenesis of sepsis and COVID-19. We further discuss the complexity of platelet activation during NETosis and the potential benefit of targeting selective or multiple NET-associated DAMPs to limit thrombo-inflammation during infection. Finally, we summarize relevant new data on this topic presented during the 2022 ISTH Congress.

Protective effects of S100A8 on sepsis mortality: Links to sepsis risk in obesity and diabetes

Obesity and diabetes are independent risk factors for death during sepsis. S100A8, an alarmin, is related to inflammation, obesity, and diabetes. Here, we examine the role of S100A8 in sepsis of obesity and diabetes models. Injection of S100A8 prolongs the survival of septic mice induced by lethal endotoxemia, Escherichia coli injection, or cecal ligation and puncture. S100A8 decrease the LPS-induced expression of proinflammatory cytokines in peritoneal macrophages by inhibiting TLR4-mediated signals in an autocrine manner. db/db, ob/ob, and western diet-fed mice demonstrate reduced upregulation of S100A8 induced by LPS treatment in both serum and peritoneal cells. These mice also show shorter survival after LPS injection, and S100A8 supplementation prolonged the survival. While myelomonocytic cells-specific S100A8-deficient mice (Lyz2 ^cre :S100A8 ^{floxed/floxed} ) exhibit shorter survival after LPS treatment, S100A8 supplementation prolonged the survival. Thus, myelomonocytic cell-derived S100A8 is crucial for protection from sepsis, and S100A8 supplementation improves sepsis, particularly in mice with obesity and diabetes.

Neutrophil Extracellular Vesicles: A Delicate Balance between Pro-Inflammatory Responses and Anti-Inflammatory Therapies

Extracellular vesicles (EVs) are released in the extracellular environment during cell activation or apoptosis. Working as signal transducers, EVs are important mediators of intercellular communication through the convoying of proteins, nucleic acids, lipids, and metabolites. Neutrophil extracellular vesicles (nEVs) contain molecules acting as key modulators of inflammation and immune responses. Due to their potential as therapeutic tools, studies about nEVs have been increasing in recent years. However, our knowledge about nEVs is still in its infancy. In this review, we summarize the current understanding of the role of nEVs in the framework of neutrophil inflammation functions and disease development. The therapeutic potential of nEVs as clinical treatment strategies is deeply discussed. Moreover, the promising research landscape of nEVs in the near future is also examined.

Involvement of Oxidative Stress in Protective Cardiac Functions of Calprotectin

Calprotectin (CLP) belonging to the S-100 protein family is a heterodimeric complex (S100A8/S100A9) formed by two binding proteins. Upon cell activation, CLP stored in neutrophils is released extracellularly in response to inflammatory stimuli and acts as damage-associated molecular patterns (DAMPs). S100A8 and S100A9 possess both anti-inflammatory and anti-bacterial properties. The complex is a ligand of the toll-like receptor 4 (TLR4) and receptor for advanced glycation end (RAGE). At sites of infection and inflammation, CLP is a target for oxidation due to its co-localization with neutrophil-derived oxidants. In the heart, oxidative stress (OS) responses and S100 proteins are closely related and intimately linked through pathophysiological processes. Our review summarizes the roles of S100A8, S100A9 and CLP in the inflammation in relationship with vascular OS, and we examine the importance of CLP for the mechanisms driving in the protection of myocardium. Recent evidence interpreting CLP as a critical modulator during the inflammatory response has identified this alarmin as an interesting drug target.

miR-24 Alleviates MI/RI by Blocking the S100A8/TLR4/MyD88/NF-kB Pathway

ABSTRACT

Although inflammation plays an important role in myocardial ischemia/reperfusion injury (MI/RI), an anti-inflammatory treatment with a single target has little clinical efficacy because of the multifactorial disorders involved in MI/RI. MicroRNAs (miR-24) can achieve multitarget regulation in several diseases, suggesting that this factor may have ideal effects on alleviation of MI/RI. In the present study, bioinformatics method was used to screen potential therapeutic targets of miR-24 associated with MI/RI. Three days before ischemia/reperfusion surgery, rats in the ischemia/reperfusion, miR-24, and adenovirus-negative control groups were injected with saline, miR-24, and adenovirus-negative control (0.1 mL of 5 × 109 PFU/mL), respectively. Myocardial enzymes, myocardial infarct size, cardiac function, and the possible molecular mechanism were subsequently analyzed. In contrast to the level of S100A8, the level of miR-24 in myocardial tissue was significantly reduced after 30 minutes of ischemia followed by reperfusion for 2 hours. Overexpression of miR-24 reduced the myocardial infarction area and improved the heart function of rats 3 days after MI/RI. Moreover, miR-24 inhibited infiltration of inflammatory cells in the peri-infarction area and decreased creatine kinase myocardial band and lactate dehydrogenase release. Interestingly, miR-24 upregulation reduced S100A8 expression, followed by inhibition of toll-like receptor 4/MyD-88/nuclear factor-k-gene binding signaling activation. In conclusion, miR-24 can alleviate MI/RI via inactivation of the S100A8/toll-like receptor 4/MyD-88/nuclear factor-k-gene binding signaling pathway.

Role of Neutrophils in Cardiac Injury and Repair Following Myocardial Infarction

Neutrophils are first-line responders of the innate immune system. Following myocardial infarction (MI), neutrophils are quickly recruited to the ischemic region, where they initiate the inflammatory response, aiming at cleaning up dead cell debris. However, excessive accumulation and/or delayed removal of neutrophils are deleterious. Neutrophils can promote myocardial injury by releasing reactive oxygen species, granular components, and pro-inflammatory mediators. More recent studies have revealed that neutrophils are able to form extracellular traps (NETs) and produce extracellular vesicles (EVs) to aggravate inflammation and cardiac injury. On the contrary, there is growing evidence showing that neutrophils also exert anti-inflammatory, pro-angiogenic, and pro-reparative effects, thus facilitating inflammation resolution and cardiac repair. In this review, we summarize the current knowledge on neutrophils’ detrimental roles, highlighting the role of recently recognized NETs and EVs, followed by a discussion of their beneficial effects and molecular mechanisms in post-MI cardiac remodeling. In addition, emerging concepts about neutrophil diversity and their modulation of adaptive immunity are discussed.

Impact of Exercise Intensity on Calprotectin Levels in Healthy Volunteers and Patients with Inflammatory Rheumatic Diseases

Exercise influences inflammatory response and immune system performance. The regular practice of a moderate activity positively regulates immunity and the inflammatory process, while intensive training depresses it and enhances inflammatory marker secretion. Calprotectin is involved in the inflammatory process, promoting neutrophil recruitment, cell degranulation, and inflammatory mediators. Furthermore, calprotectin has been associated with various inflammatory diseases, including inflammatory rheumatic diseases. The present review explores the effect of exercise on calprotectin levels in both healthy and inflammatory rheumatic conditions. Data show that the intensity duration and the type of exercise modulate calprotectin levels and participant inflammatory status. The exact role of calprotectin in the exercise response is yet unknown. Calprotectin could constitute an interesting biomarker for monitoring both the effect of exercise on the inflammatory process in healthy volunteers and the efficiency of exercise treatment programs in a patient with inflammatory rheumatic disease.

Roxithromycin attenuates inflammation via modulation of RAGE-influenced calprotectin expression in a neutrophilic asthma model

Background

Roxithromycin (RXM), a macrolide antibiotic, exhibits anti-asthmatic effects, but its specific mechanism of action remains elusive. We evaluated the effects of RXM on airway inflammation, the expression of calprotectin, and the activity of the receptor of advanced glycation end products (RAGE) to determine whether RXM alleviates inflammation by regulating RAGE activation, and thereby calprotectin expression, in neutrophilic asthma.

Methods

Male Brown Norway rats were sensitized with ovalbumin (OVA) and Freund’s complete adjuvant (FCA) mixture, followed by OVA challenge to induce neutrophilic asthma. RXM (30 mg/kg) or FPS-ZM1 (RAGE inhibitor, 1.5 mg/kg) was administered 30 min prior to each challenge. The infiltration of airway inflammatory cells and cytokines, as well as the expression of calprotectin and RAGE, was assessed.

Results

The expression of airway inflammatory cells and cytokines was found to be significantly elevated in OVA + FCA-induced rats. Increased expression of both calprotectin and RAGE was also detected in OVA + FCA-induced asthma [bronchoalveolar lavage fluid (BALF) calprotectin: 15.07±1.79 vs. 3.86±0.69 ng/mL; serum calprotectin: 20.47±1.64 vs. 9.29±1.31 ng/mL; lung tissue homogenates calprotectin: 28.82±1.01 vs. 12.02±1.38 ng/mg; BALF RAGE: 762.93±36.47 vs. 294.25±45.92 ng/mL; serum RAGE: 906.43±58.95 vs. 505.60±30.16 ng/mL; lung tissue homogenates RAGE: 1,585.24±177.59 vs. 461.53±63.40 ng/mg; all P<0.001]. However, all of these changes were interrupted by RXM and FPS-ZM1.

Conclusions

RXM exerted similar effects as the RAGE inhibitor FPS-ZM1 in terms of reducing airway inflammation and downregulating the expression of calprotectin and RAGE in a neutrophilic asthma model. Our findings provide novel insights into the mechanisms underlying the effect of RXM pretreatment on neutrophilic asthma. Furthermore, FPS-ZM1 may be useful as an intervention specific to the neutrophilic asthma phenotype.

Divalent cations influence the dimerization mode of murine S100A9 protein by modulating its disulfide bond pattern

S100A9, with its congener S100A8, belongs to the S100 family of calcium-binding proteins found exclusively in vertebrates. These two proteins are major constituents of neutrophils. In response to a pathological condition, they can be released extracellularly and become alarmins that induce both pro- and anti-inflammatory signals, through specific cell surface receptors. They also act as antimicrobial agents, mainly as a S100A8/A9 heterocomplex, through metal sequestration. The mechanisms whereby divalent cations modulate the extracellular functions of S100A8 and S100A9 are still unclear. Importantly, it has been proposed that these ions may affect both the ternary and quaternary structure of these proteins, thereby influencing their physiological properties. In the present study, we report the crystal structures of WT and C80A murine S100A9 (mS100A9), determined at 1.45 and 2.35 Å resolution, respectively, in the presence of calcium and zinc. These structures reveal a canonical homodimeric form for the protein. They also unravel an intramolecular disulfide bridge that stabilizes the C-terminal tail in a rigid conformation, thus shaping a second Zn-binding site per S100A9 protomer. In solution, mS100A9 apparently binds only two zinc ions per homodimer, with an affinity in the micromolar range, and aggregates in the presence of excess zinc. Using mass spectrometry, we demonstrate that mS100A9 can form both non-covalent and covalent homodimers with distinct disulfide bond patterns. Interestingly, calcium and zinc seem to affect differentially the relative proportion of these forms. We discuss how the metal-dependent interconversion between mS100A9 homodimers may explain the versatility of physiological functions attributed to the protein.

Association of Serum Calprotectin Concentrations with Mortality in Critically Ill and Septic Patients

Background: Calprotectin is present in the cytosol of neutrophil granulocytes and released upon activation. Fecal calprotectin is applied in the clinical management of inflammatory bowel disease whereas serum calprotectin has been discussed as a biomarker in inflammatory disorders. However, its long-term prognostic relevance in critical illness remains unclear. Our aim was to investigate serum calprotectin concentrations as a prognostic biomarker in critically ill and septic patients. Methods: Serum calprotectin concentrations were analyzed in 165 critically ill patients (108 with sepsis, 57 without sepsis) included in our observational study. Patients were enrolled upon admission to the medical intensive care unit (ICU) of the RWTH Aachen University Hospital. Calprotectin concentrations were compared to 24 healthy controls and correlated with clinical parameters, therapeutic interventions, and survival. Results: Serum calprotectin concentrations were significantly increased in ICU patients as well as in septic patients compared to respective controls (p < 0.001 for ICU patients and p = 0.001 for septic patients). Lower calprotectin concentrations were measured in patients with comorbidities i.e., coronary artery disease. Calprotectin concentrations strongly correlated with the C-reactive protein (p < 0.001) and were closely associated to parameters of mechanical ventilation (i.a. inspiratory oxygen fraction, FiO2; p < 0.001). The overall survival was significantly impaired in septic patients with high baseline calprotectin concentrations (p = 0.036). However, patients with increasing calprotectin serum concentrations within the first week of ICU admission showed an improved overall survival (p = 0.009). Conclusions: In summary, serum calprotectin concentrations are significantly increased in critically ill patients with sepsis. High calprotectin concentrations at ICU admission predict long-term mortality risk, whereas increasing calprotectin concentrations are associated with a favorable long-term outcome.

S100A8/A9 in Myocardial Infarction: A Promising Biomarker and Therapeutic Target

Myocardial infarction (MI), the main cause of cardiovascular-related deaths worldwide, has long been a hot topic because of its threat to public health. S100A8/A9 has recently attracted an increasing amount of interest as a crucial alarmin that regulates the pathogenesis of cardiovascular disease after its release from myeloid cells. However, the role of S100A8/A9 in the etiology of MI is not well understood. Here, we elaborate on the critical roles and potential mechanisms of S100A8/A9 driving the pathogenesis of MI. First, cellular source of S100A8/A9 in infarcted heart is discussed. Then we highlight the effect of S100A8/A9 heterodimer in the early inflammatory period and the late reparative period of MI as well as myocardial ischemia/reperfusion (I/R) injury. Moreover, the predictive value of S100A8/A9 for the risk of recurrence of cardiovascular events is elucidated. Therefore, this review focuses on the molecular mechanisms of S100A8/A9 in MI pathogenesis to provide a promising biomarker and therapeutic target for MI.

Emerging roles of neutrophil-borne S100A8/A9 in cardiovascular inflammation

Elevated neutrophil count is associated with higher risk of major adverse cardiac events including myocardial infarction and early development of heart failure. Neutrophils contribute to cardiac damage through a number of mechanisms, including attraction of other immune cells and release of inflammatory mediators. Recently, a number of independent studies have reported a causal role for neutrophil-derived alarmins (i.e. S100A8/A9) in inducing inflammation and cardiac injury following myocardial infarction (MI). Furthermore, a positive correlation between serum S100A8/A9 levels and major adverse cardiac events (MACE) in MI patients was also observed implying that targeting neutrophils or their inflammatory cargo could be beneficial in reducing heart failure. However, contradictory to this idea, neutrophils and neutrophil-derived S100A8/A9 also seem to play a vital role in the resolution of inflammation. Thus, a better understanding of how neutrophils balance these seemingly contrasting functions would allow us to develop effective therapies that preserve the inflammation-resolving function while restricting the damage caused by inflammation. In this review, we specifically discuss the mechanisms behind neutrophil-derived S100A8/A9 in promoting inflammation and resolution in the context of MI. We also provide a perspective on how neutrophils could be potentially targeted to ameliorate cardiac inflammation and the ensuing damage.

Elevated aldolase 1A, retrogene 1 expression induces cardiac apoptosis in rat experimental autoimmune myocarditis model

Acute myocarditis is an unpredictable heart disease that is caused by inflammation-associated cell death. Although viral infection and drug exposure are known to induce acute myocarditis, the molecular basis for its development remains undefined. Using proteomics and molecular analyses in myosin-induced rat experimental autoimmune myocarditis (EAM), we identified that elevated expression of aldolase 1A, retrogene 1 (Aldoart1) is critical to induce mitochondrial dysfunction and acute myocarditis development. Here, we demonstrate that cardiac cell death is associated with increased expressions of proapoptotic genes in addition to high levels of glucose, lactate, and triglyceride in metabolite profiling. The functional protein association network analysis also suggests that Aldoart1 upregulation correlates with high levels of dihydroxyacetone kinase and triglyceride. In H9c2 cardiac cells, lipopolysaccharides (LPS) or high glucose exposure significantly increases the cytochrome c release and the conversion of pro-caspase 3 into the cleaved form of caspase 3. We also found that LPS- or glucose-induced toxicities are almost completely reversed by siRNA-mediated knockdown of Aldoartl, which consequently increases cell viability. Together, our study strongly suggests that Aldoart1 may be involved in inducing mitochondrial apoptotic processes and can be a novel therapeutic target to prevent the onset of acute myocarditis or cardiac apoptosis.

S100 family proteins in inflammation and beyond

The S100 family proteins possess a variety of intracellular and extracellular functions. They interact with multiple receptors and signal transducers to regulate pathways that govern inflammation, cell differentiation, proliferation, energy metabolism, apoptosis, calcium homeostasis, cell cytoskeleton and microbial resistance. S100 proteins are also emerging as novel diagnostic markers for identifying and monitoring various diseases. Strategies aimed at targeting S100-mediated signaling pathways hold a great potential in developing novel therapeutics for multiple diseases. In this chapter, we aim to summarize the current knowledge about the role of S100 family proteins in health and disease with a major focus on their role in inflammatory conditions.

Viral myocarditis: a prime example for endomyocardial biopsy-guided diagnosis and therapy

Purpose of review

Myocarditis is an inflammatory disease of the cardiac muscle mainly caused by viral infection. Due to the diverse clinical presentation of myocarditis, accurate diagnosis demands simultaneous histologic, immunohistochemical and molecular biological workup of endomyocardial biopsies (EMBs) as defined by the position statement of the Working Group on Myocardial and Pericardial Diseases of the European Society of Cardiology on myocarditis.

Recent findings

Endomyocardial biopsy-based analysis of viral transcriptional activity, mRNA expression, epigenetics and region-specific protein expression analysis via imaging mass spectrometry have led to the identification of novel potential diagnostic criteria, markers with prognostic value and therapeutic targets for the treatment of viral myocarditis, opening new avenues for novel therapies, including cell therapies, as well as the use of established treatment options, be it from other indications.

Summary

Under certain clinical scenarios EMB-based analysis is required to come to a tailored individualized therapy that improves symptoms and prognosis of patients with acute and chronic viral-driven cardiac inflammation.

Myeloid-Derived Suppressor Cells Are Regulated by Estradiol and Are a Predictive Marker for IVF Outcome

In vitro fertilization (IVF) is an effective means to treat infertility, but the pregnancy rate is still unsatisfactory and reliable markers to predict pregnancy outcome are ill-defined. Myeloid-derived suppressor cell (MDSC) are critically involved in decisions related to the acceptance or rejection of foreign fetal antigens by the maternal immune system. However, factors that regulate peripheral blood MDSC during pre-pregnancy are poorly defined. Thus, the goal of this study was to assess the relationships among serum estradiol (E₂) and endothelial growth factor (VEGF) levels, MDSC ratios, and pregnancy outcome associated with IVF. Patients undergoing IVF treatment (n = 54) were recruited from January to June 2018. Levels of E₂ and VEGF were measured by ELISA, MDSC ratios among peripheral blood mononuclear cells (PBMC) were detected by flow cytometry, and the crosstalk among these parameters was analyzed. A receiver operating characteristic curve (ROC) of MDSC levels was plotted to assess this measure as an independent predictive factor for pregnancy. In addition, we analyzed the possible involvement of molecular pathways by bioinformatics. When E₂ levels were <4,000 pg/ml, MDSC proportion was positively correlated with serum E₂ and VEGF levels. However, when E₂ levels were >4,000 pg/ml, MDSC ratio and VEGF levels were negatively correlated with E₂. A ROC curve revealed that the percentage of MDSC had better sensitivity and specificity at a concentration of 8.22% (0.875 and 0.75, respectively; area under the curve (AUC) = 0.859) to predict pregnancy success, based on multiple logistic regression analysis. Furthermore, we found 12 target genes of E₂ and VEGF, and also functional genes related to MDSC, indicating potential protein-protein interactions underlying these associations. In summary, we showed that E₂, depending on its concentration, might play a dichotomous role in influencing the MDSC proportion by regulating VEGF. In IVF patients, an increased MDSC ratio among PBMC was highly correlated with elevated pregnancy rates, independent of the effects of E₂, which might provide new insight into immune-related miscarriage and IVF failure.

The role of zinc in calprotectin expression in human myeloid cells

Elevated levels of calprotectin and other inflammatory mediators have been observed in inflammatory diseases paralleling serum hypozincemia. While a role of zinc in the regulation of tumor necrosis factor α, interleukin (IL)-1β and IL-6 expression has been established, the direct interrelation of zinc and calprotectin (S100A8/S100A9 heterodimer) expression is so far missing. In the present study, we analyzed mRNA and protein levels of S100A8 and S100A9 in monocytic Mono Mac (MM)1 and early myeloid THP-1 and U937 cells to elucidate the effect of zinc deficiency on their expression. We could depict that zinc deficiency alone enhances mRNA and protein expression of calprotectin in myeloid cells, independently from maturity stage. Moreover, pre-existing zinc deficiency augmented lipopolysaccharide (LPS)-induced calprotectin expression in CD14⁺ MM1, but not in CD14^- U937 or CD14^- THP-1 cells. Zinc deficiency and LPS seem therefore to activate different intracellular pathways. Our findings suggest that zinc does not only regulate the activity of calprotectin but also its expression by human myeloid cells.

Zinc finger and interferon-stimulated genes play a vital role in TB-IRIS following HAART in AIDS

AIM

Co-infection in HIV-1 patients with Mycobacterium tuberculosis poses considerable risk of developing the immune reconstitution inflammatory syndrome (IRIS), especially upon the initiation of antiretroviral therapy (ART). Methodology & results: For transcriptomic analysis, peripheral blood mononuclear cells' whole gene expression was used from three patient groups: HIV⁺ (H), HIV-TB⁺ (HT), HIV-TB⁺ with IRIS (HTI). Pathway enrichment and functional analysis was performed before and after highly active ART. Genes in the interferon-stimulating and ZNF families maintained tight functional interaction and tilted the balance in favor of TB-IRIS.

DISCUSSION & CONCLUSION

The functional impairment of interaction between ZNF genes and interferon-stimulated genes, along with higher expression of S100A8/S100A9 genes possibly forms the genomic basis of TB-IRIS in a subset of HIV patients while on highly active ART.

Calcium-Binding Proteins S100A8 and S100A9: Investigation of Their Immune Regulatory Effect in Myeloid Cells

High expression levels of the calcium-binding proteins S100A8 and S100A9 in myeloid cells in kidney transplant rejections are associated with a favorable outcome. Here we investigated the myeloid cell subset expressing these molecules, and their function in inflammatory reactions. Different monocyte subsets were sorted from buffy coats of healthy donors and investigated for S100A8 and S100A9 expression. To characterize S100A9high and S100A9low subsets within the CD14+ classical monocyte subset, intracellular S100A9 staining was combined with flow cytometry (FACS) and qPCR profiling. Furthermore, S100A8 and S100A9 were overexpressed by transfection in primary monocyte-derived macrophages and the THP-1 macrophage cell line to investigate the functional relevance. Expression of S100A8 and S100A9 was primarily found in classical monocytes and to a much lower extent in intermediate and non-classical monocytes. All S100A9+ cells expressed human leukocyte antigen—antigen D related (HLA-DR) on their surface. A small population (<3%) of CD14+ CD11b+ CD33+ HLA-DR− cells, characterized as myeloid derived suppressor cells (MDSCs), also expressed S100A9 to high extent. Overexpression of S100A8 and S00A9 in macrophages led to enhanced extracellular reactive oxygen species (ROS) production, as well as elevated mRNA expression of anti-inflammatory IL-10. The results suggest that the calcium-binding proteins S100A8 and S100A9 in myeloid cells have an immune regulatory effect.

S100A8/A9 in Inflammation

S100A8 and S100A9 (also known as MRP8 and MRP14, respectively) are Ca²⁺ binding proteins belonging to the S100 family. They often exist in the form of heterodimer, while homodimer exists very little because of the stability. S100A8/A9 is constitutively expressed in neutrophils and monocytes as a Ca²⁺ sensor, participating in cytoskeleton rearrangement and arachidonic acid metabolism. During inflammation, S100A8/A9 is released actively and exerts a critical role in modulating the inflammatory response by stimulating leukocyte recruitment and inducing cytokine secretion. S100A8/A9 serves as a candidate biomarker for diagnosis and follow-up as well as a predictive indicator of therapeutic responses to inflammation-associated diseases. As blockade of S100A8/A9 activity using small-molecule inhibitors or antibodies improves pathological conditions in murine models, the heterodimer has potential as a therapeutic target. In this review, we provide a comprehensive and detailed overview of the distribution and biological functions of S100A8/A9 and highlight its application as a diagnostic and therapeutic target in inflammation-associated diseases.

Pathogenic Role of the Damage-Associated Molecular Patterns S100A8 and S100A9 in Coxsackievirus B3-Induced Myocarditis

BACKGROUND

The alarmins S100A8 and S100A9 are damage-associated molecular patterns, which play a pivotal role in cardiovascular diseases, inflammation, and viral infections. We aimed to investigate their role in Coxsackievirus B3 (CVB3)-induced myocarditis.

METHODS AND RESULTS

S100A8 and S100A9 mRNA expression was 13.0-fold (P=0.012) and 5.1-fold (P=0.038) higher in endomyocardial biopsies from patients with CVB3-positive myocarditis compared with controls, respectively. Elimination of CVB3 led to a downregulation of these alarmins. CVB3-infected mice developed an impaired left ventricular function and displayed an increased left ventricular S100A8 and S100A9 protein expression versus controls. In contrast, CVB3-infected S100A9 knockout mice, which are also a complete knockout for S100A8 on protein level, showed an improved left ventricular function, which was associated with a reduced cardiac inflammatory and oxidative response, and lower CVB3 copy number compared with wild-type CVB3 mice. Exogenous application of S100A8 to S100A9 knockout CVB3 mice induced a severe myocarditis similar to wild-type CVB3 mice. In CVB3-infected HL-1 cells, S100A8 and S100A9 enhanced oxidative stress and CVB3 copy number compared with unstimulated infected cells. In CVB3-infected RAW macrophages, both alarmins increased MIP-2 (macrophage inflammatory protein-2) chemokine expression, which was reduced in CVB3 S100A8 knockdown versus scrambled siRNA CVB3 cells.

CONCLUSIONS

S100A8 and S100A9 aggravate CVB3-induced myocarditis and might serve as therapeutic targets in inflammatory cardiomyopathies.

Anti-arthritic and gastroprotective activities of Ardisia crispa root partially mediated via its antioxidant effect

Background Ardisia crispa Thunb A.DC (Myrsinaceae), commonly known as "hen's eyes", has been traditionally used in treating various inflammatory diseases. The present study evaluated anti-arthritic, gastroprotective and antioxidant activities of Ardisia crispa root hexane extract (ACRH) in various animal models. Methods Anti-arthritic activity was evaluated in complete Freund adjuvant (CFA)-induced adjuvant arthritis and gastroprotective effect was studied in the ethanol-induced ulcer model in rats. ACRH was further isolated to yield quinone-rich fraction (QRF) and both were analyzed for their total phenolic content, total flavonoid content and antioxidant activities in various antioxidant assays. Both ACRH and QRF were also analyzed for the quinone composition via gas chromatography analysis. Results ACRH exerted significant reduction of IL-1β and TNF-α at a lower dose range in CFA-induced arthritis, as well as exhibited its cytoprotective effect against ethanol-induced ulcer lesion via involvement of mucosal nonprotein sulfhydryl (NP-SH) groups. ACRH also showed higher phenolic and flavonoid contents, as well as better antioxidant activities than QRF. Conclusions These findings demonstrated the plant as a potential anti-inflammatory agent, with ACRH succeeded in inhibiting both arthritic and ulcerogenic effect, possibly mediated via its antioxidant effect.

Resolution of Inflammation: What Controls Its Onset?

An effective resolution program may be able to prevent the progression from non-resolving acute inflammation to persistent chronic inflammation. It has now become evident that coordinated resolution programs initiate shortly after inflammatory responses begin. In this context, several mechanisms provide the fine-tuning of inflammation and create a favorable environment for the resolution phase to take place and for homeostasis to return. In this review, we focus on the events required for an effective transition from the proinflammatory phase to the onset and establishment of resolution. We suggest that several mediators that promote the inflammatory phase of inflammation can simultaneously initiate a program for active resolution. Indeed, several events enact a decrease in the local chemokine concentration, a reduction which is essential to inhibit further infiltration of neutrophils into the tissue. Interestingly, although neutrophils are cells that characteristically participate in the active phase of inflammation, they also contribute to the onset of resolution. Further understanding of the molecular mechanisms that initiate resolution may be instrumental to develop pro-resolution strategies to treat complex chronic inflammatory diseases, in humans. The efforts to develop strategies based on resolution of inflammation have shaped a new area of pharmacology referred to as "resolution pharmacology."

Resolution of Inflammation: What Controls Its Onset?

An effective resolution program may be able to prevent the progression from non-resolving acute inflammation to persistent chronic inflammation. It has now become evident that coordinated resolution programs initiate shortly after inflammatory responses begin. In this context, several mechanisms provide the fine-tuning of inflammation and create a favorable environment for the resolution phase to take place and for homeostasis to return. In this review, we focus on the events required for an effective transition from the proinflammatory phase to the onset and establishment of resolution. We suggest that several mediators that promote the inflammatory phase of inflammation can simultaneously initiate a program for active resolution. Indeed, several events enact a decrease in the local chemokine concentration, a reduction which is essential to inhibit further infiltration of neutrophils into the tissue. Interestingly, although neutrophils are cells that characteristically participate in the active phase of inflammation, they also contribute to the onset of resolution. Further understanding of the molecular mechanisms that initiate resolution may be instrumental to develop pro-resolution strategies to treat complex chronic inflammatory diseases, in humans. The efforts to develop strategies based on resolution of inflammation have shaped a new area of pharmacology referred to as “resolution pharmacology.”

Role of Calprotectin as a Modulator of the IL27-Mediated Proinflammatory Effect on Endothelial Cells

An underlying endothelial dysfunction plays a fundamental role in the pathogenesis of cardiovascular events and is the central feature of atherosclerosis. The protein-based communication between leukocytes and inflamed endothelial cells leading to diapedesis has been largely investigated and several key players such as IL6, TNFα, or the damage associated molecular pattern molecule (DAMP) calprotectin are now well identified. However, regarding cytokine IL27, the controversial current knowledge about its inflammatory role and the involved regulatory elements requires clarification. Therefore, we examined the inflammatory impact of IL27 on primary endothelial cells and the potentially modulatory effect of calprotectin on both transcriptome and proteome levels. A qPCR-based screening demonstrated high IL27-mediated gene expression of IL7, IL15, CXCL10, and CXCL11. Calprotectin time-dependent downregulatory effects were observed on IL27-induced IL15 and CXCL10 gene expression. A mass spectrometry-based approach of IL27 ± calprotectin cell stimulation enlightened a calprotectin modulatory role in the expression of 28 proteins, mostly involved in the mechanism of leukocyte transmigration. Furthermore, we showed evidence for STAT1 involvement in this process. Our findings provide new evidence about the IL27-dependent proinflammatory signaling which may be under the control of calprotectin and highlight the need for further investigations on molecules which might have antiatherosclerotic functions.

Anti-inflammatory role of obestatin in autoimmune myocarditis

Obestatin is a popular endogeneous peptide, known to have an autoimmune regulatory effect on energy metabolism and the gastrointestinal system. Studies regarding the anti-inflammatory effects of obestatin are scarce. The aim of this study was to show the anti-inflammatory effect of obestatin in an experimental model of autoimmune myocarditis in rats. Experimental autoimmune myocarditis was induced in Lewis rats by immunization with subcutaneous administration of porcine cardiac myosin, twice at 7-day intervals. Intraperitoneal pretreatment with obestatin (50 μg/kg) was started before the induction of myocarditis and continued for 3 weeks. The severity of myocarditis was evidenced by clinical, echocardiographic and histological findings. In addition, by-products of neutrophil activation, lipid peroxidation, inflammatory and anti-inflammatory cytokines were measured in serum. Obestatin significantly ameliorated the clinical and histopathological severity of autoimmune myocarditis. Therapeutic effects of obestatin in myocarditis were associated with reduced lipid peroxidation, suppression of polymorphonuclear leukocyte infiltration and enhancement of glutathione synthesis, inhibition of serum inflammatory and activation of anti-inflammatory cytokines. Histopathologically, the left ventricle was significantly dilated, and its wall thickened, along with widespread lymphocytic and histocytic infiltration. The myocardium was severely infiltrated with relatively large mononuclear cells. These histopathological changes were observed in lesser degrees in obestatin-treated rats. This study demonstrated a novel anti-inflammatory effect of obestatin in an experimental model of autoimmune myocarditis. Consequently, obestatin administration may represent a promising therapeutic approach for myocarditis and dilated cardiomyopathy in the future.

Mortality and morbidity in different immunization protocols for experimental autoimmune myocarditis in rats

AIM

We aimed to investigate the histological and clinical presentations of experimental autoimmune myocarditis (EAM) induced by different immunization schemes.

METHODS

Male young Lewis rats were divided into five groups immunized by porcine myocardial myosin: subcutaneously (SC) 2 mg (in two 1-mg doses on day 0 and 7), 0 mg (sham group) subcutaneously into rear footpads (RF), 0.25 mg RF, 0.5 mg RF or 1 mg RF (all RF once on day 0). On day 21, left ventricular (LV) function was assessed by cardiac magnetic resonance imaging and cardiac catheterization. The type and degree of myocardial inflammatory infiltrates were determined by conventional histology and immunohistochemistry.

RESULTS

In the SC immunized rats and in the RF sham group, we observed 0% mortality, while in the actively RF immunized rats, mortality was 20, 20 and 44% for the 0.25 mg, 0.5 mg and 1 mg myosin doses respectively. Morbidity as defined by inflammatory infiltrates on haematoxylin and eosin (HE) staining was 22% in the SC immunized rats, 0% in the RF sham group and 100% in all actively RF immunized groups. We observed augmented relative ventricle weight and spleen weight, increased LV end-diastolic pressure, reduced LV developed pressure and reduced LV ejection fraction in all with myosin-immunized RF groups without any systematic dose effect.

CONCLUSION

Subcutaneous immunization to the neck and flanks did not induce a reproducible EAM, while RF myosin administration reliably led to EAM. Lower myosin doses seem to induce the complete histological and clinical picture of EAM while being associated with lower mortality, non-specific symptoms and animal distress.

Calgranulins may contribute vascular protection in atherogenesis

S100A8, S100A9 and S100A12 are considered proinflammatory mediators of atherosclerosis. Known as calgranulins, they are major components of neutrophils and are upregulated in macrophages and foam cells. They influence leukocyte recruitment, and may propagate inflammation by binding TLR4 and/or receptor for advanced glycation endproducts (RAGE). However, the receptors for calgranulins remain an enigma; we have no evidence for TLR4 or RAGE activation by S100A8 or S100A12. Moreover, gene regulation studies suggest antiinflammatory functions for S100A8 and emerging reports indicate pleiotropic roles. Unlike S100A9, S100A8 effectively scavenges oxidants generated by the myeloperoxidase system in vivo, forming novel thiol modifications. S100A8 is also readily S-nitrosylated, stabilizing nitric oxide and transporting it to hemoglobin. S100A8-SNO reduces leukocyte transmigration in the vasculature. S-glutathionylation of S100A9 modifies its effects on leukocyte adhesion. Both S100A8 forms inhibit mast cell activation, at least partially by scavenging reactive oxygen species required for signaling. Conversely, S100A12 activates and sequesters mast cells. However S100A12 suppresses proinflammatory cytokine induction by SAA-activated monocytes and macrophages, and inhibits matrix metalloprotease activity. We propose that the abundance and types of cells expressing calgranulins in particular microenvironments, their relative concentrations and post-translational modifications may have distinct functional outcomes, including those that are protective, at different stages of atherogenesis.  

Unbiased proteomics analysis demonstrates significant variability in mucosal immune factor expression depending on the site and method of collection

Female genital tract secretions are commonly sampled by lavage of the ectocervix and vaginal vault or via a sponge inserted into the endocervix for evaluating inflammation status and immune factors critical for HIV microbicide and vaccine studies. This study uses a proteomics approach to comprehensively compare the efficacy of these methods, which sample from different compartments of the female genital tract, for the collection of immune factors. Matching sponge and lavage samples were collected from 10 healthy women and were analyzed by tandem mass spectrometry. Data was analyzed by a combination of differential protein expression analysis, hierarchical clustering and pathway analysis. Of the 385 proteins identified, endocervical sponge samples collected nearly twice as many unique proteins as cervicovaginal lavage (111 vs. 61) with 55% of proteins common to both (213). Each method/site identified 73 unique proteins that have roles in host immunity according to their gene ontology. Sponge samples enriched for specific inflammation pathways including acute phase response proteins (p = 3.37×10⁻²⁴) and LXR/RXR immune activation pathways (p = 8.82×10⁻²²) while the role IL-17A in psoriasis pathway (p = 5.98×10⁻⁴) and the complement system pathway (p = 3.91×10⁻³) were enriched in lavage samples. Many host defense factors were differentially enriched (p<0.05) between sites including known/potential antimicrobial factors (n = 21), S100 proteins (n = 9), and immune regulatory factors such as serpins (n = 7). Immunoglobulins (n = 6) were collected at comparable levels in abundance in each site although 25% of those identified were unique to sponge samples. This study demonstrates significant differences in types and quantities of immune factors and inflammation pathways collected by each sampling technique. Therefore, clinical studies that measure mucosal immune activation or factors assessing HIV transmission should utilize both collection methods to obtain the greatest representation of immune factors secreted into the female genital tract.

MRP8/14 enhances corneal susceptibility to Pseudomonas aeruginosa Infection by amplifying inflammatory responses

PURPOSE

We explored the role of myeloid-related protein 8 and 14 (MRP8/14) in Pseudomonas aeruginosa (PA) keratitis.

METHODS

MRP8/14 mRNA levels in human corneal scrapes and mouse corneas infected by PA were tested using real-time PCR. MRP8/14 protein expression in C57BL/6 (B6) corneas was confirmed using Western blot assay and immunohistochemistry. B6 mice were injected subconjunctivally with siRNA for MRP8/14, and then infected with PA. Bacterial plate counts and myeloperoxidase assays were used to determine the bacterial load and polymorphonuclear neutrophil (PMN) infiltration in infected B6 corneas. Pro-inflammatory cytokine levels in vivo and in vitro were examined with PCR and ELISA. In murine macrophage-like RAW264.7 cells, phagocytosis and bacterial killing were assessed using plate count assays, and reactive oxygen species (ROS) and nitric oxide (NO) levels were tested with flow cytometry and Griess assay, respectively.

RESULTS

MRP8/14 expression levels were increased significantly in human corneal scrapes and B6 corneas after PA infection. Silencing of MRP8/14 in B6 corneas significantly reduced the severity of corneal disease, bacterial clearance, PMN infiltration, and pro-inflammatory cytokine expression after PA infection. In vitro studies demonstrated further that silencing of MRP8/14 suppressed pro-inflammatory cytokine production, bacterial killing, and ROS production, but not phagocytosis or NO production.

CONCLUSIONS

Our study demonstrated a dual role for MRP8/14 in bacterial keratitis. Although MRP8/14 promotes bacterial clearance by enhancing ROS production, it functions more importantly as an inflammatory amplifier at the ocular surface by enhancing pro-inflammatory cytokine expression, thus contributing to the corneal susceptibility.

Noninvasive assessment of myocardial inflammation by cardiovascular magnetic resonance in a rat model of experimental autoimmune myocarditis

BACKGROUND

Limited availability of noninvasive and biologically precise diagnostic tools poses a challenge for the evaluation and management of patients with myocarditis.

METHODS AND RESULTS

The feasibility of cardiovascular magnetic resonance (CMR) imaging with magneto-fluorescent nanoparticles (MNPs) for detection of myocarditis and its effectiveness in discriminating inflammation grades were assessed in experimental autoimmune myocarditis (EAM) (n=65) and control (n=10) rats. After undergoing CMR, rats were administered with MNPs, followed by a second CMR 24 hours later. Head-to-head comparison of MNP-CMR with T(2)-weighted, early and late gadolinium enhancement CMR was performed in additional EAM (n=10) and control (n=5) rats. Contrast-to-noise ratios were measured and compared between groups. Flow cytometry and microscopy demonstrated that infiltrating inflammatory cells engulfed MNPs, resulting in altered myocardial T(2)* effect. Changes in contrast-to-noise ratio between pre- and post-MNP CMR were significantly greater in EAM rats (1.08 ± 0.10 versus 0.48 ± 0.20; P<0.001). In addition, contrast-to-noise ratio measurement in MNP-CMR clearly detected the extent of inflammation (P<0.001) except for mild inflammation. Compared with conventional CMR, MNP-CMR provided better image contrast (CNR change 8% versus 46%, P<0.001) and detectability of focal myocardial inflammation. Notably, MNP-CMR successfully tracked the evolution of myocardial inflammation in the same EAM rats.

CONCLUSIONS

Magneto-fluorescent nanoparticle CMR permitted effective visualization of myocardial inflammatory cellular infiltrates and distinction of the extent of inflammation compared with conventional CMR in a preclinical model of EAM. Magneto-fluorescent nanoparticle CMR performs best in EAM rats with at least moderate inflammatory response.

Delayed increase of S100A9 messenger RNA predicts hospital-acquired infection after septic shock

OBJECTIVE

Septic shock remains a serious disease with high mortality and increased risk of hospital-acquired infection. The prediction of outcome is of the utmost importance for selecting patients for therapeutic strategies aiming to modify the immune response. The aim of this study was to assess the capability of S100A9 messenger RNA in whole blood from patients with septic shock to predict survival and the occurrence of hospital-acquired infection.

DESIGN

Cohort study.

SETTING

Two intensive care units in a university hospital.

SUBJECTS

The study included patients with septic shock (n = 166) and healthy volunteers (n = 44).

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

For the patients with septic shock patients, overall mortality was 38% and the mean Simplified Acute Physiologic Scale II on shock onset was 52. Using quantitative reverse transcriptase-polymerase chain reactions, we found that median S100A9 messenger RNA was significantly lower in healthy volunteers than in patients with septic shock (p < .0001) between days 1 and 3 after onset of the septic shock and not significantly different between nonsurvivor and survivor patients (p = .1278). However, median S100A9 messenger RNA measured on days 7-10 was significantly higher in patients who were about to contract hospital-acquired infections compared with those who were not (p = .009). In the multivariate analysis, the S100A9 marker increased the probability of contracting hospital-acquired infections with an odds ratio of 1.12 per unit (p = .0054).

CONCLUSIONS

S100A9 messenger RNA is increased in septic shock and its delayed overexpression is associated with the occurrence of secondary hospital-acquired infection. This biomarker may be of major interest in identifying patients with increased risk of hospital-acquired infection who could benefit from targeted therapy aimed at restoring their immune functions.

The down regulation of neutrophil oxidative metabolism by S100A8 and S100A9: implication of the protease-activated receptor-2

S100A8 and S100A9 regulate polymorphonuclear neutrophils (PMNs) recruitment and represent 40% of PMN cytosolic protein weight. We have shown that S100A8/S100A9 inhibit PMN oxidative metabolism. The present study was designed to elucidate the mechanisms of this anti-oxidative effect. We hypothesized that the protease activated receptor-2 (PAR-2) played a role in the down-regulation of PMN oxidative metabolism by S100A8/S100A9. Freshly isolated PMNs were tested for their ability to oxidize dichlorofluorescin-diacetate. Functional inhibition of PAR-2 with ENMD-1068, the pepducin P2pal-21 or an antibody directed at PAR-2 cleavage/activation site, resulted in a significant inhibition of S100A8 and S100A9 anti-oxidative effect. Conversely, the controlled activation of PAR-2 potentiated S100 anti-oxidative effect. Taken together, the data indicate that the anti-oxidative effect of S100A8/A9 is initiated by PAR-2 activation. S100A8/S100A9 may therefore dampen inflammation without interfering with its initial strength. This finding opens translational possibilities to limit deleterious PMN activation with a dual PAR-2/S100 strategy.

S100A8 and S100A9 in cardiovascular biology and disease

There is recent and widespread interest in the damage-associated molecular pattern molecules S100A8 and S100A9 in cardiovascular science. These proteins have a number of interesting features and functions. For example, S100A8 and S100A9 (S100A8/A9) have both intracellular and extracellular actions, they are abundantly expressed in inflammatory and autoimmune states, primarily by myeloid cells but also by other vascular cells, and they modulate inflammatory processes, in part through Toll-like receptor 4 and the receptor for advanced glycation end products. S100A8/A9 also have anti-inflammatory and immune regulatory actions. Furthermore, increased plasma levels of S100A8/A9 predict cardiovascular events in humans, and deletion of these proteins partly protects Apoe(-)(/)(-) mice from atherosclerosis. Understanding the roles of S100A8 and S100A9 in vascular cell types and the mechanisms whereby these proteins mediate their biological effects may offer new therapeutic strategies to prevent, treat, and predict cardiovascular diseases.

S100A8/A9 complex as a new biomarker in prediction of mortality in elderly patients with severe heart failure

BACKGROUND

S100A8/A9 complex is a new inflammation-related protein and has a positive correlation with C-reaction protein level. However its role in chronic heart failure (CHF) remains unclear.

METHODS AND RESULTS

Circulating levels of S100A8/A9 complex and other biomarkers (IL-6, IL-8, TNF-α, and BNP) were measured in CHF (n = 54) and hypertensive without CHF (n = 31) as well as healthy subjects (n = 23), with follow up to 1480 days. During follow-up, cumulative mortality rate for CHF patients was 63%. Plasma levels of S100A8/A9 complex, IL-6, IL-8 and TNF-α were significantly higher in CHF than the hypertensive patients and healthy subjects. A significant positive correlation was found between S100A8/A9 complex and IL-6 and IL-8 respectively. Cox regression analysis showed that IL-6 and IL-8 were predictors for mortality for 6 months, and S100A8/A9 complex, IL-6, IL-8 and age were predictors for mortality for one year whereas BNP, TNF-α, IL-6 and IL-8 remained predictors for mortality for two years. A combination of S100A8/A9 complex and IL-6 provided powerful predictive value in mortality for both 6 and 12 months.

CONCLUSIONS

S100A8/A9 complex is a useful biomarker as a predictor for one year mortality and its combination with IL-6 is able to provide additive prognostic information in this vulnerable heart failure population in the elderly.

Effect of human immunodeficiency virus infection on S100A8/A9 inhibition of peripheral neutrophils oxidative metabolism

Neutrophils are endowed with a highly active oxidative metabolism that is crucial for their antimicrobial functions but can produce oxidative conditions disruptive to the host. Opportunistic infections associated with HIV disease and ex vivo studies of neutrophils from HIV patients suggest that neutrophil dysfunctions significantly contribute to HIV disease. The calcium-binding proteins S100A8 and S100A9 are abundant cytosolic constituents of human neutrophils. Our previous work has shown that S100A8 and S100A9 inhibit neutrophil oxidative metabolism. In this study, we tested the hypothesis that neutrophils from HIV infected subjects respond differently to S100A8 and S100A9 when compared to neutrophils isolated from control HIV naive subjects. Neutrophils, freshly isolated from whole blood, were tested in a 96-well plate assay for their ability to oxidize the DCFH-DA probe. The neutrophils from HIV+ and HIV- subjects were stimulated with LPS and inhibited with recombinant S100A8 and S100A9. Our data indicate that when compared to neutrophils isolated from HIV- subjects, neutrophils from HIV+ subjects display an exaggerated response to LPS and a diminished response to S100A8 and S100A9 inhibition. Our data support our hypothesis and signify that, in HIV disease, dysregulated neutrophil responses to endotoxins stimulation and S100A8/A9 inhibition may contribute to a higher risk for oxidative stress associated ailments. The mechanism for the observed differences in neutrophil response and their biological significance in the course of HIV disease should be addressed in further studies.

Inflammation-associated S100 proteins: new mechanisms that regulate function

This review focuses on new aspects of extracellular roles of the calgranulins. S100A8, S100A9 and S100A12 are constitutively expressed in neutrophils and induced in several cell types. The S100A8 and S100A9 genes are regulated by pro- and anti-inflammatory mediators and their functions may depend on cell type, mediators within a particular inflammatory milieu, receptors involved in their recognition and their post-translational modification. The S100A8 gene induction in macrophages is dependent on IL-10 and potentiated by immunosuppressive agents. S100A8 and S100A9 are oxidized by peroxide, hypochlorite and nitric oxide (NO). HOCl generates intra-chain sulfinamide bonds; stronger oxidation promotes cross-linked forms that are seen in human atheroma. S100A8 is >200-fold more sensitive to oxidative cross-linking than low-density lipoprotein and may reduce oxidative damage. S100A8 and S100A9 can be S-nitrosylated. S100A8-SNO suppresses mast cell activation and inflammation in the microcirculation and may act as an NO transporter to regulate vessel tone in inflammatory lesions. S100A12 activates mast cells and is a monocyte and mast cell chemoattractant; a G-protein-coupled mechanism may be involved. Structure-function studies are discussed in relation to conservation and divergence of functions in S100A8. S100A12 induces cytokines in mast cells, but not monocytes/macrophages. It forms complexes with Zn(2+) and, by chelating Zn(2+), S100A12 significantly inhibits MMPs. Zn(2+) in S100A12 complexes co-localize with MMP-9 in foam cells in atheroma. In summary, S100A12 has pro-inflammatory properties that are likely to be stable in an oxidative environment, because it lacks Cys and Met residues. Conversely, S100A8 and S100A9 oxidation and S-nitrosylation may have important protective mechanisms in inflammation.