CCR1 and CC chemokine ligand 5 interactions exacerbate innate immune responses during sepsis

The causal effects of circulating cytokines on sepsis: a Mendelian randomization study

Background

In observational studies, sepsis and circulating levels of cytokines have been associated with unclear causality. This study used Mendelian randomization (MR) to identify the causal direction between circulating cytokines and sepsis in a two-sample study.

Methods

An MR analysis was performed to estimate the causal effect of 41 cytokines on sepsis risk. The inverse-variance weighted random-effects method, the weighted median-based method, and MR-Egger were used to analyze the data. Heterogeneity and pleiotropy were assessed using MR-Egger regression and Cochran's Q statistic.

Results

Genetically predicted beta-nerve growth factor (OR = 1.12, 95% CI [1.037-1.211], P = 0.004) increased the risk of sepsis, while RANTES (OR = 0.92, 95% CI [0.849-0.997], P = 0.041) and fibroblast growth factor (OR = 0.869, 95% CI [0.766-0.986], P = 0.029) reduced the risk of sepsis. These findings were robust in extensive sensitivity analyses. There was no clear association between the other cytokines and sepsis risk.

Conclusion

The findings of this study demonstrate that beta-nerve growth factor, RANTES, and fibroblast growth factor contribute to sepsis risk. Investigations into potential mechanisms are warranted.

Causal association of circulating cytokines with sepsis: a Mendelian randomization study

Background

Observational studies have reported an association between circulating cytokines and sepsis. However, the precise causal relationship between these factors remains unclear. The objective of this study was to explore the causal link between circulating cytokines and sepsis using genetic data within the framework of Mendelian Randomization (MR).

Methods

We performed a two-sample MR analysis to investigate this causality relationship in individuals of European ancestry. The publicly available genome-wide association studies (GWAS) statistics were used. We selected eligible instrumental single nucleotide polymorphisms (SNPs) that were significantly related to the circulating cytokines. Multiple MR analysis approaches were carried out, which included inverse variance weighted (IVW), Weighted Median, MR-Egger, Weighted Mode, Simple Mode, and MR pleiotropy residual sum and outlier (MR-PRESSO) methods.

Results

We found evidence to support the causal role of genetically predicted circulating levels on decreased risk of sepsis, including RANTES (OR = 0.920, 95% CI: 0.849-0.997, P = 0.041) and basic fibroblast growth factor (basic-FGF) (OR = 0.869, 95% CI: 0.766-0.986, P = 0.029). Additionally, MR analysis positive causal association of between beta-nerve growth factor (β-NGF) and sepsis (OR = 1.120, 95% CI: 1.037-1.211, P = 0.004). The results of MR-Egger, Weighted Median, Weighted Mode, and Simple Mode methods were consistent with the IVW estimates. Sensitivity analysis showed no horizontal pleiotropy to bias the causal estimates.

Conclusion

This MR study provides first novel evidence that genetically predicted causal association of circulating levels of RANTES, basic-FGF, and β-NGF with altered sepsis risk. The findings shed light on the potential involvement of these cytokines in sepsis pathogenesis. Although requiring additional confirmation, the results contribute new insights into cytokine mediators in sepsis and suggest promising future research directions.

High-Dose Vitamin B6 (Pyridoxine) Displays Strong Anti-Inflammatory Properties in Lipopolysaccharide-Stimulated Monocytes

Vitamin B6 is shown to have anti-inflammatory properties, which makes it an interesting nutraceutical agent. Vitamin B6 deficiency is well established as a contributor to inflammatory-related conditions, whilst B6 supplementation can reverse these inflammatory effects. There is less information available regarding the effects of high-dose vitamin B6 supplementation as a therapeutic agent. This study set out to examine the effects of high-dose vitamin B6 on an LPS-stimulated monocyte/macrophage cell population via an analysis of protein and gene expression using an RT2 profiler PCR array for Human Innate and Adaptive Immune responses. It was identified that high-dose vitamin B6 has a global anti-inflammatory effect on lipopolysaccharide-induced inflammation in monocyte/macrophage cells by downregulating the key broad-spectrum inflammatory mediators CCL2, CCL5, CXCL2, CXCL8, CXCL10, CCR4, CCR5, CXCR3, IL-1β, IL-5, IL-6, IL-10, IL-18, IL-23-a, TNF-α, CSF2, DDX58, NLRP3, NOD1, NOD2, TLR-1 -2 -4 -5 -7 -8 -9, MYD88, C3, FOXP3, STAT1, STAT3, STAT6, LYZ, CASP-1, CD4, HLA-E, MAPK1, MAPK8 MPO, MX-1, NF-κβ, NF-κβ1A, CD14, CD40, CD40LG, CD86, Ly96, ICAM1, IRF3, ITGAM, and IFCAM2. The outcomes of this study show promise regarding vitamin B6 within the context of a potent broad-spectrum anti-inflammatory mediator and could prove useful as an adjunct treatment for inflammatory-related diseases.

Single-cell Sequence Analysis Combined with Multiple Machine Learning to Identify Markers in Sepsis Patients: LILRA5

Sepsis is a disease with a very high mortality rate, mainly involving an immune-dysregulated response due to bacterial infection. Most studies are currently limited to the whole blood transcriptome level; however, at the single cell level, there is still a great deal unknown about specific cell subsets and disease markers. We obtained 29 peripheral blood single-cell sequencing data, including 66,283 cells from 10 confirmed samples of sepsis infection and 19 healthy samples. Cells related to the sepsis phenotype were identified and characterized by the "scissor" method. The regulatory relationships of sepsis-related phenotype cells in the cellular communication network were clarified using the "cell chat" method. The least absolute shrinkage and selection operator (LASSO), support vector machine (SVM), and random forest (RF) were used to identify sepsis signature genes of diagnostic value. External validation was performed using multiple datasets from the GEO database (GSE28750, GSE185263, GSE57065) and 40 clinical samples. Bayesian algorithm was used to calculate the regulatory network of LILRA5 co-expressed genes. The stability of atenolol-targeting LILRA5 was determined by molecular docking techniques. Ultimately, action trajectory and survival analyses demonstrate the effectiveness of atenolol-targeted LILRA5 in treating patients with sepsis. We successfully identified 1215 healthy phenotypic cells and 462 sepsis phenotypic cells. We focused on 447 monocytes of the sepsis phenotype. Among the cellular communications, there were a large number of differences between these cells and other immune cells showing a significant inflammatory phenotype compared to the healthy phenotypic cells. Together, the three machine learning algorithms identified the LILRA5 marker gene in sepsis patients, and validation results from multiple external datasets as well as real-world clinical samples demonstrated the robust diagnostic performance of LILRA5. The AUC values of LILRA5 in the external datasets GSE28750, GSE185263, and GSE57065 could reach 0.875, 0.940, and 0.980, in that order. Bayesian networks identified a large number of unknown regulatory relationships for LILRA5 co-expression. Molecular docking results demonstrated the possibility of atenolol targeting LILRA5 for the treatment of sepsis. Behavioral trajectory analysis and survival analysis demonstrate that atenolol has a desirable therapeutic effect. LILRA5 is a marker gene in sepsis patients, and atenolol can stably target LILRA5.

Ginkgolic acid promotes inflammation and macrophage apoptosis via SUMOylation and NF-κB pathways in sepsis

Background

Excessive inflammation and increased apoptosis of macrophages contribute to organ damage and poor prognosis of sepsis. Ginkgolic acid (GA) is a natural constituent extracted from the leaves of Ginkgo biloba, that can regulate inflammation and apoptosis. The present study aims to investigate the potential effect of GA in treating sepsis and its possible mechanisms.

Materials and methods

Here, a classic septic mice model and a lipopolysaccharide (LPS)-induced RAW 264.7 inflammation model were established. Cytokines in serum and culture supernatant were detected by ELISA, and the mRNA levels of them were examined by PCR. Hematoxylin and eosin (H&E) staining was performed to determine histopathological changes in liver, lung and kidney. Bacterial burden in the blood, peritoneal lavage fluids (PLFs) and organs were observed on Luria-Bertani agar medium. Flow cytometry and western blotting was used to detect apoptosis and the expression level of apoptosis related molecules, respectively. Moreover, the levels of SUMOylation were detected by western blotting. The activity of NF-κB p65 was assessed by immunofluorescence staining and western blotting.

Results

The result showed that GA promoted inflammatory responses, reduced bacterial clearance, aggravated organ damage, and increased mortality in septic mice. GA increased apoptosis in peritoneal macrophages (PMs) and RAW 264.7 cells. Meanwhile, GA inhibited SUMOylation and increased the nuclear translocation of NF-κB p65 as well as its phosphorylation level.

Conclusion

Collectively, GA promotes inflammation and macrophage apoptosis in sepsis, which may be mediated by inhibiting the SUMOylation process and increasing NF-κB p65 activity.

Single-cell RNA sequencing reveals rebalancing of immunological response in patients with periodontitis after non-surgical periodontal therapy

Background

Periodontitis is a major inflammatory disease of the oral mucosa that is not limited to the oral cavity but also has systemic consequences. Although the importance of chronic periodontitis has been emphasized, the systemic immune response induced by periodontitis and its therapeutic effects remain elusive. Here, we report the transcriptomes of peripheral blood mononuclear cells (PBMCs) from patients with periodontitis.

Methods

Using single-cell RNA sequencing, we profiled PBMCs from healthy controls and paired pre- and post-treatment patients with periodontitis. We extracted differentially expressed genes and biological pathways for each cell type and calculated activity scores reflecting cellular characteristics. Intercellular crosstalk was classified into therapy-responsive and -nonresponsive pathways.

Results

We analyzed pan-cellular differentially expressed genes caused by periodontitis and found that most cell types showed a significant increase in CRIP1, which was further supported by the increased levels of plasma CRIP1 observed in patients with periodontitis. In addition, activated cell type-specific ligand-receptor interactions, including the BTLA, IFN-γ, and RESISTIN pathways, were prominent in patients with periodontitis. Both the BTLA and IFN-γ pathways returned to similar levels in healthy controls after periodontal therapy, whereas the RESISTIN pathway was still activated even after therapy.

Conclusion

These data collectively provide insights into the transcriptome changes and molecular interactions that are responsive to periodontal treatment. We identified periodontitis-specific systemic inflammatory indicators and suggest unresolved signals of non-surgical therapy as future therapeutic targets.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12967-022-03702-2.

Identification of a novel sepsis prognosis model and analysis of possible drug application prospects: Based on scRNA-seq and RNA-seq data

Sepsis is a disease with a high morbidity and mortality rate. At present, there is a lack of ideal biomarker prognostic models for sepsis and promising studies using prognostic models to predict and guide the clinical use of medications. In this study, 71 differentially expressed genes (DEGs) were obtained by analyzing single-cell RNA sequencing (scRNA-seq) and transcriptome RNA-seq data, and Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment pathway analyses were performed on these genes. Then, a prognosis model with CCL5, HBD, IFR2BP2, LTB, and WFDC1 as prognostic signatures was successfully constructed after univariate LASSO regression analysis and multivariate Cox regression analysis. Kaplan-Meier (K-M) survival analysis, receiver operating characteristic (ROC) time curve analysis, internal validation, and principal component analysis (PCA) further validated the model for its high stability and predictive power. Furthermore, based on a risk prediction model, gene set enrichment analysis (GSEA) showed that multiple cellular functions and immune function signaling pathways were significantly different between the high- and low-risk groups. In-depth analysis of the distribution of immune cells in healthy individuals and sepsis patients using scRNA-seq data revealed immunosuppression in sepsis patients and differences in the abundance of immune cells between the high- and low-risk groups. Finally, the genetic targets of immunosuppression-related drugs were used to accurately predict the potential use of clinical agents in high-risk patients with sepsis.

Screening of Sepsis Biomarkers Based on Bioinformatics Data Analysis

Methods

Gene expression profiles of GSE13904, GSE26378, GSE26440, GSE65682, and GSE69528 were obtained from the National Center for Biotechnology Information (NCBI). The differentially expressed genes (DEGs) were searched using limma software package. Gene Ontology (GO) functional analysis, Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment analysis, and protein-protein interaction (PPI) network analysis were performed to elucidate molecular mechanisms of DEGs and screen hub genes.

Results

A total of 108 DEGs were identified in the study, of which 67 were upregulated and 41 were downregulated. 15 superlative diagnostic biomarkers (CCL5, CCR7, CD2, CD27, CD274, CD3D, GNLY, GZMA, GZMH, GZMK, IL2RB, IL7R, ITK, KLRB1, and PRF1) for sepsis were identified by bioinformatics analysis.

Conclusion

15 hub genes (CCL5, CCR7, CD2, CD27, CD274, CD3D, GNLY, GZMA, GZMH, GZMK, IL2RB, IL7R, ITK, KLRB1, and PRF1) have been elucidated in this study, and these biomarkers may be helpful in the diagnosis and therapy of patients with sepsis.

Pretreatment with 6-Gingerol Ameliorates Sepsis-Induced Immune Dysfunction by Regulating the Cytokine Balance and Reducing Lymphocyte Apoptosis

Sepsis is characterized by an initial net hyperinflammatory response, followed by a period of immunosuppression, termed immunoparalysis. During this immunosuppressive phase, patients may have difficulty eradicating invading pathogens and are susceptible to life-threatening secondary hospital-acquired infections. Due to progress in antimicrobial treatment and supportive care, most patients survive early sepsis. Mortality is more frequently attributed to subsequent secondary nosocomial infections and multiorgan system failure. 6-Gingerol is the major pharmacologically active component of ginger. Although it is known to exhibit a variety of biological activities, including anti-inflammation and antioxidation, the role of 6-gingerol in sepsis-induced immune dysfunction remains elusive. Thus, we investigated whether 6-gingerol improves septic host response to infections during sepsis. 6-Gingerol-treated mice showed significantly lower mortality in polymicrobial sepsis induced by cecal ligation and puncture LPS via enhanced bacterial clearance in the peritoneum, blood, and organs (liver, spleen, and kidney) and inhibited the production of TNF-α and IL-6 in TLR2 and/or TLR4-stimulated macrophages. In addition, we demonstrated that survival improvement of secondary infection following septic insult was associated with an initial response of enhanced neutrophil numbers and function at the infection site, reduced apoptosis of immune cells, and a shift from a T helper cell type 2 (Th2) to a T helper cell type 1 (Th1) cytokine balance in the hypoinflammation phase. Our overall findings suggest that 6-gingerol potentially restores sepsis-induced immune dysfunction by shifting the balance of Th1/Th2 and by regulating apoptosis of immune cells.

Leveraging publicly available coronavirus data to identify new therapeutic targets for COVID-19

Many important questions remain regarding severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2), the viral pathogen responsible for COVID-19. These questions include the mechanisms explaining the high percentage of asymptomatic but highly infectious individuals, the wide variability in disease susceptibility, and the mechanisms of long-lasting debilitating effects. Bioinformatic analysis of four coronavirus datasets representing previous outbreaks (SARS-CoV-1 and MERS-CoV), as well as SARS-CoV-2, revealed evidence of diverse host factors that appear to be coopted to facilitate virus-induced suppression of interferon-induced innate immunity, promotion of viral replication and subversion and/or evasion of antiviral immune surveillance. These host factors merit further study given their postulated roles in COVID-19-induced loss of smell and brain, heart, vascular, lung, liver, and gut dysfunction.

Role of Fractalkine in promoting inflammation in sepsis-induced multiple organ dysfunction

OBJECTIVE

Fractalkine, CX3CL1, is involved in the directional movement of chemokine cells, immune response, inflammatory response, tissue repair, and other processes. However, its role in sepsis is not well known.

METHODS

We measured circulating Fractalkine in adult patients with sepsis. Effects of Fractalkine on the survival, inflammation, tissue injury, and bacterial clearance were assessed using the WT or CX3CL^-/- murine model of cecal ligation and puncture (CLP)-induced sepsis.

RESULTS

Serum Fractalkine concentrations were significantly elevated in adult patients with sepsis compared to healthy adults. Increased Fractalkine correlated positively with the number of blood leukocytes and the level of inflammatory cytokines, including IL-6, IL-1β, IL-17A, IFN-γ, and TNF-α, and correlated negatively with IL-10 in clinical sepsis. Recombinant Fractalkine impaired survival whereas Fractalkine gene knockout or anti-Fractalkine antibody improved survival in the murine model of CLP-induced sepsis. Fractalkine administration increased inflammatory response, evident by higher levels of cytokines (TNF-α, IL-1β, IL-17A, IFN-γ, and IL-6 but not IL-10), and tissue damage (lung, liver, and kidney) in CLP-induced sepsis. Fractalkine reduced bacterial clearance in CLP-induced polymicrobial sepsis by reducing macrophage or neutrophil phagocytosis and intracellular elimination of E. coli.

CONCLUSIONS

Fractalkine aggravates sepsis by increasing inflammation and decreasing bacterial clearance, and is a potential tool for anti-sepsis therapy.

Chemokine receptors coordinately regulate macrophage dynamics and mammary gland development

Macrophages are key regulators of developmental processes, including those involved in mammary gland development. We have previously demonstrated that the atypical chemokine receptor ACKR2 contributes to the control of ductal epithelial branching in the developing mammary gland by regulating macrophage dynamics. ACKR2 is a chemokine-scavenging receptor that mediates its effects through collaboration with inflammatory chemokine receptors (iCCRs). Here, we reveal reciprocal regulation of branching morphogenesis in the mammary gland, whereby stromal ACKR2 modulates levels of the shared ligand CCL7 to control the movement of a key population of CCR1-expressing macrophages to the ductal epithelium. In addition, oestrogen, which is essential for ductal elongation during puberty, upregulates CCR1 expression on macrophages. The age at which girls develop breasts is decreasing, which raises the risk of diseases including breast cancer. This study presents a previously unknown mechanism controlling the rate of mammary gland development during puberty and highlights potential therapeutic targets.

Proteomic analysis of lipopolysaccharide activated human monocytes

Monocytes are key mediators of innate immunity and comprise an important cellular defence against invading pathogens. However, exaggerated or dysregulated monocyte activation can lead to severe immune-mediated pathology such as sepsis or chronic inflammatory diseases. Thus, detailed insight into the molecular mechanisms of monocyte activation is essential to understand monocyte-driven inflammatory pathologies. We therefore investigated the global protein changes in human monocytes during lipopolysaccharide (LPS) activation to mimic bacterial activation. Purified human monocytes were stimulated with LPS for 17 h and analyzed by state-of-the-art liquid chromatography tandem mass spectrometry (LC-MS/MS). The label-free quantitative proteome analysis identified 2746 quantifiable proteins of which 101 had a statistically significantly different abundance between LPS-stimulated cells and unstimulated controls. Additionally, 143 proteins were exclusively identified in either LPS stimulated cells or unstimulated controls. Functional annotation clustering demonstrated that LPS, most significantly, regulates proteasomal- and lysosomal proteins but in opposite directions. Thus, seven proteasome subunits were upregulated by LPS while 11 lysosomal proteins were downregulated. Both systems are critically involved in processing of proteins for antigen-presentation and together with LPS-induced regulation of CD74 and tapasin, our data suggest that LPS can skew monocytic antigen-presentation towards MHC class I rather than MHC class II. In summary, this study provides a sensitive high throughput protein analysis of LPS-induced monocyte activation and identifies several LPS-regulated proteins not previously described in the literature which can be used as a source for future studies.

CCL5 Promotes Resolution-Phase Macrophage Reprogramming in Concert with the Atypical Chemokine Receptor D6 and Apoptotic Polymorphonuclear Cells

The engulfment of apoptotic polymorphonuclear cells (PMN) during the resolution of inflammation leads to macrophage reprogramming culminating in reduced proinflammatory and increased anti-inflammatory mediator secretion. The atypical chemokine receptor D6/ACKR2 is expressed on apoptotic PMN and plays an important role in regulating macrophage properties during and after engulfment. In this study, we found that the inflammatory chemokine CCL5 is mostly retained (75%) during the resolution of zymosan A peritonitis in mice. Moreover, this chemokine is secreted by resolution-phase macrophages (2.5 ng/ml) and promotes their reprogramming in vivo in D6+/+ mice (2-fold increase in IL-10/IL-12 ratio) but not their D6-/- counterparts. In addition, CCL5 enhanced macrophage reprogramming ex vivo exclusively when bound to D6+/+ apoptotic PMN. Signaling through p38MAPK and JNK in reprogrammed macrophages was enhanced by CCL5-bound apoptotic PMN (3.6-4 fold) in a D6-dependent manner, and was essential for reprogramming. Thus, CCL5 exerts a novel proresolving role on macrophages when acting in concert with apoptotic PMN-expressed D6.

A polymorphism in CCR1/CCR3 is associated with narcolepsy

Etiology of narcolepsy-cataplexy involves multiple genetic and environmental factors. While the human leukocyte antigen (HLA)-DRB1*15:01-DQB1*06:02 haplotype is strongly associated with narcolepsy, it is not sufficient for disease development. To identify additional, non-HLA susceptibility genes, we conducted a genome-wide association study (GWAS) using Japanese samples. An initial sample set comprising 409 cases and 1562 controls was used for the GWAS of 525,196 single nucleotide polymorphisms (SNPs) located outside the HLA region. An independent sample set comprising 240 cases and 869 controls was then genotyped at 37 SNPs identified in the GWAS. We found that narcolepsy was associated with a SNP in the promoter region of chemokine (C-C motif) receptor 1 (CCR1) (rs3181077, P=1.6×10(-5), odds ratio [OR]=1.86). This rs3181077 association was replicated with the independent sample set (P=0.032, OR=1.36). We measured mRNA levels of candidate genes in peripheral blood samples of 38 cases and 37 controls. CCR1 and CCR3 mRNA levels were significantly lower in patients than in healthy controls, and CCR1 mRNA levels were associated with rs3181077 genotypes. In vitro chemotaxis assays were also performed to measure monocyte migration. We observed that monocytes from carriers of the rs3181077 risk allele had lower migration indices with a CCR1 ligand. CCR1 and CCR3 are newly discovered susceptibility genes for narcolepsy. These results highlight the potential role of CCR genes in narcolepsy and support the hypothesis that patients with narcolepsy have impaired immune function.

CCR1 plays a critical role in modulating pain through hematopoietic and non-hematopoietic cells

Inflammation is associated with immune cells infiltrating into the inflammatory site and pain. CC chemokine receptor 1 (CCR1) mediates trafficking of leukocytes to sites of inflammation. However, the contribution of CCR1 to pain is incompletely understood. Here we report an unexpected discovery that CCR1-mediated trafficking of neutrophils and CCR1 activity on non-hematopoietic cells both modulate pain. Using a genetic approach (CCR1^−/− animals) and pharmacological inhibition of CCR1 with selective inhibitors, we show significant reductions in pain responses using the acetic acid-induced writhing and complete Freund's adjuvant-induced mechanical hyperalgesia models. Reductions in writhing correlated with reduced trafficking of myeloid cells into the peritoneal cavity. We show that CCR1 is highly expressed on circulating neutrophils and their depletion decreases acetic acid-induced writhing. However, administration of neutrophils into the peritoneal cavity did not enhance acetic acid-induced writhing in wild-type (WT) or CCR1^−/− mice. Additionally, selective knockout of CCR1 in either the hematopoietic or non-hematopoietic compartments also reduced writhing. Together these data suggest that CCR1 functions to significantly modulate pain by controlling neutrophil trafficking to the inflammatory site and having an unexpected role on non-hematopoietic cells. As inflammatory diseases are often accompanied with infiltrating immune cells at the inflammatory site and pain, CCR1 antagonism may provide a dual benefit by restricting leukocyte trafficking and reducing pain.

YB-1 is an early and central mediator of bacterial and sterile inflammation in vivo

In vitro studies identified Y-box-binding protein (YB)-1 as a key regulator of inflammatory mediators. In this study, we observed increased levels of secreted YB-1 in sera from sepsis patients. This led us to investigate the in vivo role of YB-1 in murine models of acute peritonitis following LPS injection, in sterile renal inflammation following unilateral ureteral obstruction, and in experimental pyelonephritis. LPS injection enhanced de novo secretion of YB-1 into the urine and the peritoneal fluid of LPS-treated mice. Furthermore, we could demonstrate a significant, transient upregulation and posttranslational modification (phosphorylation at serine 102) of YB-1 in renal and inflammatory cells. Increased renal cytoplasmic YB-1 amounts conferred enhanced expression of proinflammatory chemokines CCL2 and CCL5. Along these lines, heterozygous YB-1 knockout mice (YB-1(+/d)) that display 50% reduced YB-1 levels developed significantly lower responses to both LPS and sterile inflammation induced by unilateral ureteral obstruction. This included diminished immune cell numbers due to impaired migration propensities and reduced chemokine expression. YB-1(+/d) mice were protected from LPS-associated mortality (20% mortality on day 3 versus 80% in wild-type controls); however, immunosuppression in YB-1(+/d) animals resulted in 50% mortality. In conclusion, our findings identify YB-1 as a major, nonredundant mediator in both systemic and local inflammatory responses.

Characterization of the LPS-induced inflammation of the adrenal gland in mice

Systemic administration of endotoxin, which closely mimics the bacteria-induced systemic inflammatory response syndrome (SIRS) can ultimately lead to organ failure. Adrenal gland insufficiency is frequently diagnosed in critically ill patients; however, the underlying mechanisms are still unclear. In the present study, we studied comprehensively the characteristics of adrenal gland dysregulation, including inflammation, leukocyte infiltration and cell death in the adrenal glands in the course of LPS-induced systemic inflammation in mice. LPS enhanced expression of many proinflammatory cytokines, chemokines and adhesion molecules, which resulted in rapid recruitment of leukocytes into the adrenal gland. Furthermore, LPS-mediated inflammation was associated with increased apoptosis of adrenocortical and chromaffin cells. Our results performed in mice, suggest that LPS-induced adrenal gland inflammation and cell death might be mechanisms potentially involved in the adrenal gland dysfunction in patients with sepsis.

Ketoprofen impairs immunosuppression induced by severe sepsis and reveals an important role for prostaglandin E2

The mechanism of immunosuppression induced by severe sepsis is not fully understood. The production of prostaglandin E2 (PGE2) during sepsis is well known, but its role in long-term consequences of sepsis has not been explored. The current study evaluates the role of PGE2 in the development of immunosuppression secondary to sepsis and its potential as therapeutic target. Cecal ligation and puncture was used as an experimental model for sepsis induction in Balb/c and C57BL/6 mice. Immunosuppression was evaluated by the response to secondary infection with Aspergillus fumigatus in sepsis survivors. The role of prostanoids was evaluated in vivo and in vitro by treatment with the cyclooxygenase inhibitor ketoprofen. Balb/c mice were more susceptible than C57BL/6 to severe sepsis and to secondary infection, with a greater mortality rate. Prostaglandin E2 concentrations found in bronchoalveolar lavage in sham and cecal ligation and puncture group after fungal challenge were much higher in Balb/c than in C57BL/6 mice. Ketoprofen treatment improved survival of septic Balb/c mice subjected to secondary infection, while also enhancing macrophage phagocytosis and neutrophil recruitment to the lungs. We identified a pivotal role for PGE2 acting on EP4 receptors in modulating cytokine production differentially by sham and septic macrophages. Furthermore, sepsis also altered key enzymes in PGE2 synthesis and degradation. Our results indicate the involvement of PGE2 in severe sepsis-induced immunosuppression. Inhibition of PGE2 production represents an attractive target to improve innate immune response against secondary infection in the immunocompromised host.

Role of an iron-dependent transcriptional regulator in the pathogenesis and host response to infection with Streptococcus pneumoniae

Iron is a critical cofactor for many enzymes and is known to regulate gene expression in many bacterial pathogens. Streptococcus pneumoniae normally inhabits the upper respiratory mucosa but can also invade and replicate in lungs and blood. These anatomic sites vary considerably in both the quantity and form of available iron. The genome of serotype 4 pneumococcal strain TIGR4 encodes a putative iron-dependent transcriptional regulator (IDTR). A mutant deleted at idtr (Δidtr) exhibited growth kinetics similar to parent strain TIGR4 in vitro and in mouse blood for up to 48 hours following infection. However, Δidtr was significantly attenuated in a murine model of sepsis. IDTR down-regulates the expression of ten characterized and putative virulence genes in nasopharyngeal colonization and pneumonia. The host cytokine response was significantly suppressed in sepsis with Δidtr. Since an exaggerated inflammatory response is associated with a poor prognosis in sepsis, the decreased inflammatory response could explain the increased survival with Δidtr. Our results suggest that IDTR, which is dispensable for pneumococcal growth in vitro, is associated with regulation of pneumococcal virulence in specific host environments. Additionally, IDTR ultimately modulates the host cytokine response and systemic inflammation that contributes to morbidity and mortality of invasive pneumococcal disease.

Endotoxins affect bioactivity of chitosan derivatives in cultures of bone marrow-derived human mesenchymal stem cells

Biomaterials research has been expanding over the last decade, in part to provide improved medical devices for the treatment of orthopedic tissue injuries. In the quest to provide the best performance combined with low cost for medical implants, an increasing number of non-chemists have entered the field of biomaterials research without the profound knowledge of chemistry needed to understand the complex interaction mechanisms and characteristics of natural substances. Likewise, non-biologists often lack understanding when it comes to the presence of the contaminating biota frequently found in natural substances. This lack of knowledge by researchers in the field, combined with sensitive in vitro cell-based assays, can lead to inaccurate evaluation of biomaterials. Hence, there should be both an active effort to assemble multi-disciplinary teams and a genuine concern for the possible effects of contamination on in vitro assays. Here, we show that the presence of bacterial endotoxins in chitosan derivatives can result in false-positive results, profoundly altering product performance in in vitro assays. False-positive results through uncritical use of natural substances in vitro can be avoided by proper endotoxin testing and careful evaluation of cytokine secretion patterns.

RANTES gene polymorphisms (-403G>A and -28C>G) associated with hepatitis B virus infection in a Saudi population

Besides the host immune response, genetic and environmental factors play crucial roles in the manifestation of hepatitis B virus (HBV) infection. "Regulated on activation normal T-cell expressed and secreted" factor (RANTES) plays a vital role in CD4(+), CD8(+) T-lymphocyte and dendritic cell activation and proliferation in inflammation. Single nucleotide polymorphisms (SNPs) in the RANTES gene are associated with several viral and non-viral diseases. Association studies have invariably indicated a lack of association between RANTES gene SNPs and HBV infection in ethnic populations, even though RANTES gene SNPs exhibit distinct ethnic distributions. Despite the high prevalence of HBV infections in Saudi Arabia, no studies have been made concerning a possible relationship between RANTES gene polymorphisms and susceptibility to and progression of HBV infection. We examined -403G>A and -28C>G RANTES gene variants in 473 healthy controls and 484 HBV patients in ethnic Saudi populations. Significant differences were found in the genotype and allele distributions of the SNPs between the controls and the HBV patients. Both SNPs were significantly linked to viral clearance in these subjects. Our data demonstrate for the first time in a Saudi population, a relationship between the RANTES gene polymorphisms and the clinical course of HBV infection and underscore the importance of evaluating the genetic background of the affected individual to determine how it may affect disease progression.

Chemokine receptor CCR1 disruption limits renal damage in a murine model of hemolytic uremic syndrome

Shiga toxin (Stx)-producing Escherichia coli is the main etiological agent that causes hemolytic uremic syndrome (HUS), a microangiopathic disease characterized by hemolytic anemia, thrombocytopenia, and acute renal failure. Although direct cytotoxic effects on endothelial cells by Stx are the primary pathogenic event, there is evidence that indicates the inflammatory response mediated by polymorphonuclear neutrophils and monocytes as the key event during HUS development. Because the chemokine receptor CCR1 participates in the pathogenesis of several renal diseases by orchestrating myeloid cell kidney infiltration, we specifically addressed the contribution of CCR1 in a murine model of HUS. We showed that Stx type 2-treated CCR1(-/-) mice have an increased survival rate associated with less functional and histological renal damage compared with control mice. Stx type 2-triggered neutrophilia and monocytosis and polymorphonuclear neutrophil and monocyte renal infiltration were significantly reduced and delayed in CCR1(-/-) mice compared with control mice. In addition, the increase of the inflammatory cytokines (tumor necrosis factor-α and IL-6) in plasma was delayed in CCR1(-/-) mice compared with control mice. These data demonstrate that CCR1 participates in cell recruitment to the kidney and amplification of the inflammatory response that contributes to HUS development. Blockade of CCR1 could be important to the design of future therapies to restrain the inflammatory response involved in the development of HUS.

The dynamics of the early inflammatory response in double-hit burn and sepsis animal models

Severe burn trauma is generally associated with bacterial infections, which causes a more persistent inflammatory response with an ongoing hypermetabolic and catabolic state. This complex biological response, mediated by chemokines and cytokines, can be more severe when excessive interactions between the mediators take place. In this study, the early inflammatory response following the cecum ligation and puncture (CLP) or its corresponding control treatment (sham-CLP or SCLP) in burn (B) male rats was analyzed by measuring 23 different cytokines and chemokines. Cytokines and chemokines, including MCP-1, IP-10, leptin, TNF-α, MIP-1α, IL-18, GMCSF, RANTES and GCSF were significantly altered in both B+CLP and B+SCLP groups. IL-10 and IL-6 were significantly up-regulated in the B+CLP group when compared to the B+SCLP group. Down regulation of leptin and IP-10 concentrations were found to be related to surgery and/or infection. IL-18 and MCP-1 were elevated in all groups including previously published single injury models receiving similar treatments. In this study, insult-specific mediators with their characteristic temporal patterns were elucidated in double hit models.

Cecal ligation and puncture: the gold standard model for polymicrobial sepsis?

Sepsis is a serious medical condition characterized by dysregulated systemic inflammatory responses followed by immunosuppression. To study the pathophysiology of sepsis, diverse animal models have been developed. Polymicrobial sepsis induced by cecal ligation and puncture (CLP) is the most frequently used model because it closely resembles the progression and characteristics of human sepsis. Here we summarize the role of several immune components in the pathogenesis of sepsis induced by CLP. However, several therapies proposed on the basis of promising results obtained by CLP could not be translated to the clinic. This demonstrates that experimental sepsis models do not completely mimic human sepsis. We propose several strategies to narrow the gap between experimental sepsis models and clinical sepsis, including targeting factors that contribute to the immunosuppressive phase of sepsis, and reproducing the heterogeneity of human patients.

Comparison of the cytokine and chemokine dynamics of the early inflammatory response in models of burn injury and infection

The inflammatory response, and its subsequent resolution, are the result of a very complex cascade of events originating at the site of injury or infection. When the response is severe and persistent, Systemic Inflammatory Response Syndrome can set in, which is associated with a severely debilitating systemic hypercatabolic state. This complex behavior, mediated by cytokines and chemokines, needs to be further explored to better understand its systems properties and potentially identify multiple targets that could be addressed simultaneously. In this context, short term responses of serum cytokines and chemokines were analyzed in two types of insults: rats receiving a "sterile" cutaneous dorsal burn on 20% of the total body surface area (TBSA); rats receiving a cecum ligation and puncture treatment (CLP) to induce infection. Considering the temporal variability observed in the baseline corresponding to the control group, the concept of area under the curve (AUC) was explored to assess the dynamic responses of cytokines and chemokines. MCP-1, GROK/KC, IL-12, IL-18 and IL-10 were observed in both burn and CLP groups. While IL-10 concentration was only increased in the burn group, Eotaxin was only elevated in CLP group. It was also observed that Leptin and IP-1 concentrations were decreased in both CLP and sham-CLP groups. The link between the circulating protein mediators and putative transcription factors regulating the cytokine/chemokine gene expression was explored by searching the promoter regions of cytokine/chemokine genes in order to characterize and differentiate the inflammatory responses based on the dynamic data. Integrating multiple sources together with the bioinformatics tools identified mediators sensitive to type and extent of injury, and provided putative regulatory mechanisms. This is essential to gain a better understanding for the important regulatory points that can be used to modulate the inflammatory state at molecular level.

Retinoid X receptor alpha controls innate inflammatory responses through the up-regulation of chemokine expression

The retinoid X receptor alpha (RXRalpha) plays a central role in the regulation of many intracellular receptor signaling pathways and can mediate ligand-dependent transcription by forming homodimers or heterodimers with other nuclear receptors. Although several members of the nuclear hormone receptor superfamily have emerged as important regulators of macrophage gene expression, the existence in vivo of an RXR signaling pathway in macrophages has not been established. Here, we provide evidence that RXRalpha regulates the transcription of the chemokines Ccl6 and Ccl9 in macrophages independently of heterodimeric partners. Mice lacking RXRalpha in myeloid cells exhibit reduced levels of CCL6 and CCL9, impaired recruitment of leukocytes to sites of inflammation, and lower susceptibility to sepsis. These studies demonstrate that macrophage RXRalpha plays key roles in the regulation of innate immunity and represents a potential target for immunotherapy of sepsis.

Substance P in polymicrobial sepsis: molecular fingerprint of lung injury in preprotachykinin-A-/- mice

Deletion of mouse preprotachykinin-A (PPTA), which encodes mainly for neuropeptide substance P, has been shown to protect against lung injury and mortality in sepsis. This study explored microarray-based differential gene expression profiles in mouse lung tissue 8 h after inducing microbial sepsis and the effect of PPTA gene deletion. A range of genes differentially expressed (more than two-fold) in microarray analysis was assessed, comparing wild-type and PPTA-knockout septic mice with their respective sham controls, and the data were further validated. Genetic deletion of substance P resulted in a significantly different expression profile of genes involved in inflammation and immunomodulation after the induction of sepsis, compared with wild-type mice. Interestingly, apart from the various proinflammatory mediators, the antiinflammatory cytokine interleukin-1 receptor antagonist gene (IL1RN) was also elevated much more in PPTA(-/-) septic mice. In addition, semiquantitative RT-PCR analysis supported the microarray data. The microarray data imply that the elevated levels of inflammatory gene expression in the early stages of sepsis in PPTA-knockout mice are possibly aimed to resolve the infection without excessive immunosuppression. As scientists are divided over the effects of pro- and antiinflammatory mediators in sepsis, it seems prudent to define the status depending on a complete genome profile. This is the first report exploring pulmonary gene expression profiles using microarray analysis in PPTA-knockout mice subjected to cecal ligation and puncture-induced sepsis and providing additional biological insight into the protection received against lung injury and mortality.

Plasma cytokine profiles in preprotachykinin-A knockout mice subjected to polymicrobial sepsis

During the course of polymicrobial sepsis, a range of pro- and antiinflammatory cytokines are produced by the host immune system. Successful recovery from sepsis involves striking a balance between these counteracting cytokines. We herein investigated the circulating cytokine profiles in preprotachykinin-A knockout (PPTA(-/-)) mice, which have been found to be protected significantly against microbial sepsis, by employing multiplexed bead-based suspension arrays for the measurement of 18 plasma cytokines. Four sets of PPTA(-/-) and wild-type mice, each with six mice, were subjected to cecal ligation and puncture-induced sepsis or a sham procedure and were killed at 1, 5, 8 and 24 h post surgery. The cytokine profiles revealed, rather interestingly, that both pro- and antiinflammatory cytokines were elevated in the knockout group in response to a septic challenge. The higher systemic levels of both pro- and antiinflammatory cytokines in PPTA(-/-) septic mice was similar to the increase that we observed earlier in lung tissue of PPTA(-/-) mice after induction of sepsis. Thus, elevated levels of both pro- and antiinflammatory mediators may act simultaneously and help to resolve the infectious assault at the early stages of sepsis without excessively damaging the host tissue in PPTA(-/-) mice. In addition, our results underline the importance of comprehensive clinical analysis of multiple biomarkers to provide a better prognostic tool.

Blockade of CD137 signaling counteracts polymicrobial sepsis induced by cecal ligation and puncture

Sepsis, a leading cause of death worldwide, involves proinflammatory responses and inefficient bacterial clearance. Previously, we have shown that CD137 (4-1BB), a member of the tumor necrosis factor receptor superfamily, plays critical roles in eradicating infective Listeria monocytogenes, a gram-positive bacterium, and that stimulation of CD137 protects mice from sepsis-induced death. In this study, we unexpectedly found that CD137 activation aggravated polymicrobial sepsis due to mixed gram-positive and gram-negative bacterial infection induced by cecal ligation and puncture (CLP). CD137-deficient (CD137(-/-)) mice showed significantly lower mortality than CD137-sufficient (CD137(+/+)) mice in the CLP model. Administration of an agonistic anti-CD137 monoclonal antibody (MAb) to CD137(+/+) mice decreased their survival in this infection model, while administration of a blocking anti-CD137 ligand MAb (TKS-1) to such mice increased their survival. CD137(-/-) mice and TKS-1-treated CD137(+/+) mice had lower levels of chemokines/proinflammatory cytokines (monocyte chemoattractant protein 1, interleukin-6 [IL-6], tumor necrosis factor alpha, IL-12) and an anti-inflammatory cytokine (IL-10), exhibited improved bacterial clearance in the peritoneum, liver, and blood, and had greater numbers of infiltrated peritoneal neutrophils and macrophages in the CLP model than control mice. Our data suggest that CD137 activation aggravates polymicrobial sepsis induced by CLP.

Marked upregulation of cholesterol 25-hydroxylase expression by lipopolysaccharide

During screening of genes upregulated by lipopolysaccharide (LPS; endotoxin) treatment of bone marrow-derived mouse macrophages, it was unexpectedly found that cholesterol 25-hydroxylase (Ch25h) was strongly upregulated. Treatment of macrophages with 10 ng/ml of LPS for 2 h resulted in a 35-fold increase in the expression of Ch25h. In contrast, LPS treatment did not increase the expression of Cyp27a1 or Cyp7b1. The increased Ch25h expression was found to be independent of Myeloid differentiation protein 88 signaling but dependent on Toll-like receptor 4 signaling. LPS treatment of macrophages caused a 6- to 7-fold increase in cellular 25-hydroxycholesterol concentration. When macrophages were treated with increasing concentrations of 25-hydroxycholesterol, a dose-dependent release of CCL5 into the culture medium was observed. Intravenous injection of LPS in eight healthy volunteers resulted in an increase in plasma 25-hydroxycholesterol concentration. The possibility is discussed that 25-hydroxycholesterol may have a role in the inflammatory response, in addition to its more established role in the regulation of cholesterol homeostasis.

Chemokine receptor and ligand upregulation in the diaphragm during endotoxemia and Pseudomonas lung infection

Sepsis-induced diaphragmatic inflammation has been associated with respiratory failure, but the role of chemokines in this process has not been evaluated. Here we sought to study the local expression and molecular regulation of the chemokines, regulated upon activation normal T cell expressed and secreted (RANTES) and macrophage inflammatory protein (MIP)-1α, in the murine diaphragm during sepsis. Constitutive expression levels of RANTES and MIP-1α, as well as their receptors, CCR1 and CCR5, were significantly higher in diaphragm than limb muscle. Sepsis was induced by acute lipopolysaccharide (LPS) delivery or subacutely by intratracheal administration of live Pseudomonas aeruginosa bacteria. Both sepsis models triggered a marked upregulation of RANTES and MIP-1α in the diaphragm. In vitro, stimulation of diaphragmatic muscle cells with LPS also led to RANTES upregulation. Inhibition of the NF-kB pathway using pharmacologic or dominant negative genetic approaches blocked the LPS-induced RANTES upregulation, while free radical scavengers had no effect. We conclude that sepsis leads to greatly increased expression of RANTES, MIP-1α and their cognate receptors in the diaphragm. Manipulation of the NF-kB pathway and other regulators of chemokine expression in the diaphragm could represent a novel method for mitigating the skeletal muscle inflammatory response associated with sepsis-induced diaphragmatic dysfunction.

Administration of exogenous fractalkine, a CX3C chemokine, is capable of modulating inflammatory response in cecal ligation and puncture-induced sepsis

Fractalkine (FTK) is a unique member of the CX3C chemokine family by acting through the CX3CR1 receptor. Membrane-bound FTK acts like an adhesion molecule, whereas soluble FTK (sFTK) acts as a classic chemokine ligand. Whether this chemokine plays a role in sepsis is still not clear. Using a mouse model of cecal ligation and puncture (CLP)-induced sepsis, we found that FTK levels were elevated in plasma 24 h after CLP. Reverse transcription-polymerase chain reaction results showed that FTK messenger RNA levels were upregulated, whereas CX3CR1 messenger RNA levels were downregulated in lungs after CLP procedure. To study the role of FTK in lung injury during sepsis, we injected exogenous sFTK into the mice before the CLP procedure. We found that plasma FTK levels were further elevated by sFTK. Mice that were injected with FTK had a lower myeloperoxidase activity in lungs compared with the CLP group. Furthermore, macrophage inflammatory protein 2, IL-1beta, and IL-6 levels in lungs were reduced after the injection of FTK. Treatment with sFTK also attenuated lung morphological changes in histological sections. To find out whether sFTK had an effect on leukocyte rolling and adherence, intravital microscope was used. Results showed that sFTK significantly attenuated leukocyte adhesion but had little effect on leukocyte rolling in mesenteric microcirculation. Taken together, our findings suggest that FTK may be a novel chemokine that modulates neutrophil infiltration and chemokine and cytokine production during sepsis.

Interaction between RANTES promoter variant and CCR5Delta32 favors recovery from hepatitis B

Recovery from acute hepatitis B virus (HBV) infection occurs in 95% of adult-acquired infections. A 32-bp deletion in CCR5 (CCR5Delta32), which encodes for a nonfunctional receptor, increases the likelihood of recovery. Using 181 subjects with persistent HBV infection and 316 who had recovered, we tested the hypothesis that an epistatic interaction between functional polymorphisms in RANTES (a CCR5 ligand) and CCR5 impacts recovery. Specific models designed to assess individual contributions of compound genotypes demonstrated that the only combination associated with recovery from an HBV infection was RANTES -403A with CCR5Delta32 (odds ratio 0.36, p = 0.02). Because the phenotypic consequence of -403A is reported to be higher levels of RANTES, we propose a model in which excess RANTES in combination with low CCR5 favors recovery from an HBV infection, which will require validation through functional testing.

A key role for CC chemokine receptor 1 in T-cell-mediated respiratory inflammation

CC chemokine receptor 1 (CCR1) is found on a variety of cells in the immune system and has been shown to play an important role in the host response to pathogens. These studies used a murine model of virus-induced exacerbation of allergic airway disease to examine the role of CCR1 on T cells associated with immune responses taking place in the lung. Lungs of virally exacerbated allergic animals contained elevated levels of interferon-gamma and interleukin-13 and increased levels of CCR1 ligands CCL3 and CCL5. CCR1 expression on T cells was increased in virally exacerbated allergic animals over the level observed in mice sensitized to allergen or exposed to viral infection alone. Using mice deficient for CCR1, we observed decreased airway hyperreactivity and Th2 cytokine production from CD4(+) T cells when this receptor was absent. Transfer studies demonstrated that neither CD4(+) nor CD8(+) T cells from CCR1(-/-) mice migrated to the lymph node as efficiently as wild-type T cells. Intracellular cytokine staining in wild-type mice revealed that CCR1(+) CD4(+) and CD8(+) T cells are associated with interleukin-13 production. Thus, these studies identify CCR1 as a potential target for alleviating T-cell accumulation during exacerbation of asthmatic disease.

The chemokine CCL6 promotes innate immunity via immune cell activation and recruitment

Septic syndrome is a consequence of innate immune failure. Recent studies showed that the CC chemokine CCL6 enhanced antimicrobial immunity during experimental sepsis through an unknown mechanism. The present study demonstrates that transgenic CCL6 expression abolishes mortality in a septic peritonitis model via the modulation of resident peritoneal cell activation and, more importantly, through the recruitment of IFN-producing NK cells and killer dendritic cells into the peritoneum. Thus, CCL6 attenuates the immune failure during sepsis, in part, through a protective type 1-cytokine mediated mechanism.

A systemic granulomatous response to Schistosoma mansoni eggs alters responsiveness of bone-marrow-derived macrophages to Toll-like receptor agonists

Macrophages play a pivotal role in innate and acquired immune responses to Schistosoma mansoni. Classical (M1) or alternative (M2) activation states of these cells further delineate their roles in tissue damage through innate immunity or fibrotic remodeling, respectively. In the present study, we addressed the following question: Does systemic Th2-type cytokine polarization evoked by S. mansoni affect macrophage differentiation and activation? To this end, we analyzed bone marrow-derived macrophages from mice with S. mansoni egg-induced pulmonary granulomas and unchallenged (or naïve) mice to determine their activation state and their response to specific TLR agonists, including S. mansoni egg antigens. Unlike naïve macrophages, macrophages from Th2-polarized mice constitutively expressed significantly higher "found in inflammatory zone-1" (FIZZ1) and ST2 (M2 markers) and significantly lower NO synthase 2, CCL3, MIP-2, TNF-alpha, and IL-12 (M1 markers). Also, compared with naïve macrophages, Th2-polarized macrophages exhibited enhanced responses to the presence of specific TLR agonists, which consistently induced significantly higher levels of gene and protein levels for M2 and M1 markers in these cells. Together, these data show that signals received by bone marrow precursors during S. mansoni egg-induced granuloma responses dynamically alter the development of macrophages and enhance the TLR responsiveness of these cells, which may ultimately have a significant effect on the pulmonary granulomatous response.

The effect of aging and caloric restriction on murine CD8+ T cell chemokine receptor gene expression

Background

The mechanism explaining the increased disease susceptibility in aging is not well understood. CD8+ T cells are crucial in anti-viral and anti-tumor responses. Although the chemokine system plays a critical role in CD8+ T cell function, very little is known about the relationship between aging and the T cell chemokine system.

Results

In this study we have examined the effect of aging on murine CD8+ T cell chemokine receptor gene expression. Freshly isolated splenic CD8+ T cells from old C57BL/6 mice were found to have higher CCR1, CCR2, CCR4, CCR5 and CXCR5, and lower CCR7 gene expression compared to their younger cohort. Anti-CD3/anti-CD28 stimulation elicited a similar robust chemokine receptor response from young and old CD8+ T cells. Western blot analyses confirmed elevated protein level of CCR4 and CCR5 in aged CD8+ T cells. Increases in T cell CCR1 and CCR5 expression also correlate to increased in vitro chemotaxis response to macrophage-inflammatory protein-1 α(MIP-1α). Finally, caloric restriction selectively prevents the loss of CD8+ T cell CCR7 gene expression in aging to the level that is seen in young CD8+ T cells.

Conclusion

These findings are consistent with the notion that aging exists in a state of low grade pro-inflammatory environment. In addition, our results provide a potential mechanism for the reported aging-associated impaired T cell lymphoid homing and allograft response, and reduced survival in sepsis.

CCR1/CCL5 (RANTES) receptor-ligand interactions modulate allogeneic T-cell responses and graft-versus-host disease following stem-cell transplantation

Acute graft-versus-host disease (GVHD) and leukemic relapse are serious complications of allogeneic stem-cell transplantation (SCT). Recruitment of activated T cells to host target tissues or sites of leukemic infiltration (graft-versus-leukemia [GVL]) is likely mediated by chemokine receptor-ligand interactions. We examined the contribution of donor cell CCR1 expression to the development of GVHD and GVL using a well-established murine SCT model (B6 --> B6D2F1) and CCR1-deficient mice (CCR1(-/-)). Allo-SCT with CCR1(-/-) donor cells significantly reduced systemic and target organ GVHD severity, and CCR1 expression on both T cells and accessory cells contributed to GVHD mortality. Significant GVL activity was preserved following CCR1(-/-) SCT, but the survival advantage diminished with increasing tumor burden. We then explored the effects of CCR1 expression on allo-specific T-cell responses. Although cytolytic effector function was maintained on a per-cell basis, T-cell proliferation and IFNgamma secretion were significantly reduced both in vivo and in vitro. T-cell function was partially dependent on interactions between CCR1 and CCL5. Collectively, these data demonstrate that CCR1 expression on donor cells contributes to the development of both GVHD and GVL, and suggest that CCR1/CCL5 receptor-ligand interactions modulate allo-specific T-cell responses occurring in this context.

The chemokine receptor CCR6 is an important component of the innate immune response

In our initial studies we found that naïve CCR6-deficient (CCR6(-/-)) C57BL/6 mice possessed significantly lower number of both F4/80(+) macrophages and dendritic cells (DC), but higher number of B cells in the peritoneal cavity, as compared to naïve wild type (WT) controls. Furthermore, peritoneal macrophages isolated from CCR6(-/-) mice expressed significantly lower levels of inflammatory cytokines and nitric oxide following lipopolysaccharide (LPS)stimulation, as compared to WT macrophages. In a severe experimental peritonitis model induced by cecal ligation and puncture (CLP), CCR6(-/-) mice were protected when compared with WT controls. At 24 h following the induction of peritonitis, CCR6(-/-) mice exhibited significantly lower levels of inflammatory cytokines/chemokines in both the peritoneal cavity and blood. Interestingly, DC recruitment into the peritoneal cavity was impaired in CCR6(-/-) mice during the evolution of CLP-induced peritonitis. Peritoneal macrophages isolated from surviving CCR6(-/-) mice 3 days after CLP-induced peritonitis exhibited an enhanced LPS response compared with similarly treated WT peritoneal macrophages. These data illustrate that CCR6 deficiency alters the innate response via attenuating the hyperactive local and systemic inflammatory response during CLP-induced peritonitis.

Polymorphisms in chemokine receptor genes and susceptibility to Kawasaki disease

Kawasaki disease (KD) is an acute vasculitis occurring in young children. Its aetiology is unknown, but an infectious agent is assumed. Increased levels of proinflammatory cytokines and chemokines have been reported in KD. Genetic variation in these genes and the receptors for these genes could influence the regulation of cytokines and chemokines. In a case-control study of 170 Dutch Caucasian KD patients and 300 healthy Dutch Caucasian controls, common genetic variants in chemokine receptor genes CCR3, CCR2, CCR5, CX3CR1, CXCR1 and CXCR2 were analysed. Of the eight studied single nucleotide polymorphisms (SNPs) in the CCR3-CCR2-CCR5 gene cluster, four showed a significant association with susceptibility to KD. Moreover the CCR5-Delta32 was observed with an allele frequency of 10.7% in the control population compared to 6.5% in the KD patients (P = 0.04). Two haplotypes of the CCR3-CCR2-CCR5 gene-cluster appear to be at risk haplotypes for KD and one a protective haplotype. No association was observed with the studied SNPs in CX3CR1, CXCR1 and CXCR2. In conclusion, in a Dutch cohort of KD patients an association of KD occurrence with common genetic variants in the chemokine receptor gene-cluster CCR3-CCR2-CCR5 was observed.

Neurokinin-1 receptor antagonist treatment protects mice against lung injury in polymicrobial sepsis

Earlier work from our laboratory has suggested a role for the neuropeptide substance P (SP) in inducing lung injury in sepsis. In that study, mice lacking the preprotachykinin-A gene, which encodes for SP, were protected against lung injury in sepsis. To further substantiate the role of SP in sepsis and to study its mechanism, we have evaluated the effect of SR140333, a SP receptor antagonist, on lung injury in sepsis, which was induced in male Swiss mice by cecal ligation and puncture (CLP). Sham-operated animals received the same surgical procedure, except CLP. Vehicle or SR140333 (1 mg/kg, s.c.) was administered to CLP mice 30 min before or 1 h after the CLP. Eight hours after surgery, lung tissue was collected and analyzed for myeloperoxidase (MPO) activity, chemokines, cytokines, and adhesion molecules. The CLP procedure alone caused a significant increase in the lung levels of MIP-2, MCP-1, IL-1beta, IL-6, ICAM-1, E- and P-selectin, and MPO activity when compared with sham-operated mice. SR140333 injected 30 min before or 1 h after CLP significantly attenuated the increased lung MPO activity and levels of MIP-2, MCP-1, IL-1beta, IL-6, ICAM-1, and E- and P-selectin compared with CLP-operated mice injected with the vehicle. Histological evaluation of the lung sections further supported the beneficial effect of SR140333 on lung inflammation. Therefore, SP receptor antagonism can be a potential therapeutic target in polymicrobial sepsis, and this effect is brought about via reduction in leukocyte recruitment.

Treatment with BX471, a CC chemokine receptor 1 antagonist, attenuates systemic inflammatory response during sepsis

Sepsis is a complex clinical syndrome resulting from a harmful host inflammatory response to infection. Chemokines and their receptors play a key role in the pathogenesis of sepsis. BX471 is a potent nonpeptide CC chemokine receptor-1 (CCR1) antagonist in both human and mouse. The aim of the present study was to evaluate the effect of prophylactic and therapeutic treatment with BX471 on cecal ligation and puncture-induced sepsis in the mouse and to investigate the underlying mechanisms. In sepsis induced by cecal ligation and puncture, treatment with BX471 significantly protected mice against lung and liver injury by attenuating MPO activity, an indicator of neutrophil recruitment in lungs and livers and attenuating lung and liver morphological changes in histological sections. Blocking CCR1 by BX471 also downregulated ICAM-1, P-selectin, and E-selectin expression at mRNA and protein levels in lungs and livers compared with placebo-treated groups. These findings suggest that blockage of CCR1 by specific antagonist may represent a promising strategy to prevent disease progression in sepsis.

Treatment with BX471, a nonpeptide CCR1 antagonist, protects mice against acute pancreatitis-associated lung injury by modulating neutrophil recruitment

OBJECTIVES

Chemokines and their receptors play a key role in the pathogenesis of acute pancreatitis. BX471 is a potent nonpeptide CC chemokine receptor 1 antagonist in both human and mouse. The aim of the present study was to evaluate the effect of prophylactic and therapeutic treatment with BX471 on experimental acute pancreatitis in the mouse and to investigate the underlying mechanisms.

METHODS

Acute pancreatitis was induced in mice by hourly intraperitoneal injection of cerulein. BX471 was administered either prophylactically or therapeutically, and pancreatic inflammation and lung injury were assessed. The expression of intercellular adhesion molecule 1, P-selectin, and E-selectin was studied by reverse transcriptase-polymerase chain reaction and immunohistochemistry.

RESULTS

In cerulein-induced acute pancreatitis, treatment with BX471 significantly protected mice against lung injury associated with cerulein-induced pancreatitis by attenuating myeloperoxidase activity, an indicator of neutrophil recruitment, and lung morphological changes in histological sections. Treatment with BX471 had little effect on pancreatic damage. Blocking CC chemokine receptor 1 by BX471 also down-regulated intercellular adhesion molecule 1, P-selectin, and E-selectin expression at mRNA and protein levels in both lungs and pancreas compared with vehicle-treated groups.

CONCLUSIONS

These findings suggest that interfering with neutrophil migration and activation by targeting CC chemokine receptor 1 may represent a promising strategy to prevent disease progression in acute pancreatitis.