Circulating Neutrophil Extracellular Trap (NET)-forming neutrophils in rheumatoid arthritis exacerbation are majority dual endothelin-1/signal peptide receptor (DEspR)+ subtype.

Neutrophil extracellular traps (NETs) are associated with rheumatoid arthritis pathogenesis and severity. Since homeostatic NET-forming neutrophils [NET+Ns] have beneficial roles in defense against pathogens, their distinction from pro-injury [NET+N] subtypes is important, especially if they are to be therapeutically-targeted. Having identified circulating, pro-injury DEspR+CD11b+ [NET+Ns] in patients with neutrophilic secondary tissue injury, we determined whether DEspR+ [NET+Ns] are present in RA-flares. Whole blood samples of patients with RA-flares on maintenance therapy (n=6), were analyzed by flow cytometry (FCM) and immunofluorescence cytology followed by semi-automated quantitative confocal microscopy (qIFC). We assessed clinical parameters, levels of neutrophils and [NET+Ns], and plasma S100A8/A9. qIFC detected circulating DEspR+CD11b+ neutrophils and [NET+Ns] in RA-flare patients but not healthy controls. DEspR+ [NET+Ns] were positive for citrullinated histone H3 (citH3+), extruded DNA, decondensed but recognizable polymorphic nuclei, and [NET+N] doublet-interactions in mostly non-ruptured NET-forming neutrophils. Circulating DNA+/DEspR+/CD11b+/citH3+ microvesicles (netMVs) were observed. FCM detected increased %DEspR+CD11b+ neutrophils and DEspR+ cell-cell doublets whose levels trended with DAS28 scores, as did plasma S100A8/A9 levels. This study identifies circulating DEspR+/CD11b+ neutrophils and [NET+Ns] in RA-flare patients on maintenance therapy. Detection of circulating DEspR+citH3+ [NET+Ns] and netMVs indicate a systemic neutrophilic source of citH3-antigen concordant with multi-joint RA pathogenesis. Increased S100A8/A9 alarmin levels are associated with cell injury and released upon NET-formation. As a ligand for TLR4, S100A8/A9 forms a positive feedback loop for TLR4-induced DEspR+ neutrophils. These data identify DEspR+ neutrophils and [NET+Ns] in RA pathogenesis as a potential biomarker and/or therapeutic target.

Platelet TLR7 is essential for the formation of platelet-neutrophil complexes and low-density neutrophils in lupus nephritis.

OBJECTIVES: Platelets and low-density neutrophils (LDNs) are major players in the immunopathogenesis of SLE. Despite evidence showing the importance of platelet-neutrophil complexes (PNCs) in inflammation, little is known about the relationship between LDNs and platelets in SLE. We sought to characterize the role of LDNs and Toll-like receptor 7 (TLR7) in clinical disease. METHODS: Flow cytometry was used to immunophenotype LDNs from SLE patients and controls. The association of LDNs with organ damage was investigated in a cohort of 290 SLE patients. TLR7 mRNA expression was assessed in LDNs and high-density neutrophils (HDNs) using publicly available mRNA sequencing datasets and our own cohort using RT-PCR. The role of TLR7 in platelet binding was evaluated in platelet-HDN mixing studies using TLR7-deficient mice and Klinefelter syndrome patients. RESULTS: SLE patients with active disease have more LDNs, which are heterogeneous and more immature in patients with evidence of kidney dysfunction. LDNs are platelet bound, in contrast to HDNs. LDNs settle in the peripheral blood mononuclear cell (PBMC) layer due to the increased buoyancy and neutrophil degranulation from platelet binding. Mixing studies demonstrated that this PNC formation was dependent on platelet-TLR7 and that the association results in increased NETosis. The neutrophil:platelet ratio is a useful clinical correlate for LDNs, and a higher NPR is associated with past and current flares of LN. CONCLUSIONS: LDNs sediment in the upper PBMC fraction due to PNC formation, which is dependent on the expression of TLR7 in platelets. Collectively, our results reveal a novel TLR7-dependent crosstalk between platelets and neutrophils that may be an important therapeutic opportunity for LN.

LAT1 enables T cell activation under inflammatory conditions.

The aim of this study was to assess the L-type amino acid transporter-1 (LAT1) as a possible therapeutic target for rheumatoid arthritis (RA). Synovial LAT1 expression in RA was monitored by immunohistochemistry and transcriptomic datasets. The contribution of LAT1 to gene expression and immune synapse formation was assessed by RNA-sequencing and total internal reflection fluorescent (TIRF) microscopy, respectively. Mouse models of RA were used to assess the impact of therapeutic targeting of LAT1. LAT1 was strongly expressed by CD4+ T cells in the synovial membrane of people with active RA and the level of expression correlated with levels of ESR and CRP as well as DAS-28 scores. Deletion of LAT1 in murine CD4+ T cells inhibited the development of experimental arthritis and prevented the differentiation of CD4+ T cells expressing IFN-γ and TNF-α, without affecting regulatory T cells. LAT1 deficient CD4+ T cells demonstrated reduced transcription of genes associated with TCR/CD28 signalling, including Akt1, Akt2, Nfatc2, Nfkb1 and Nfkb2. Functional studies using TIRF microscopy revealed a significant impairment of immune synapse formation with reduced recruitment of CD3ζ and phospho-tyrosine signalling molecules in LAT1 deficient CD4+ T cells from the inflamed joints but not the draining lymph nodes of arthritic mice. Finally, it was shown that a small molecule LAT1 inhibitor, currently undergoing clinical trials in man, was highly effective in treating experimental arthritis in mice. It was concluded that LAT1 plays a critical role in activation of pathogenic T cell subsets under inflammatory conditions and represents a promising new therapeutic target for RA.

Neutrophil function following treatment of psoriatic arthritis patients with secukinumab: altered cytokine signalling but no impairment of host defence.

OBJECTIVES: Identifying that dysfunction of the IL-23/17 axis underlies PsA has led to the development of effective targeted therapies such as the IL-17A inhibitor secukinumab. As IL-17A stimulates the secretion of neutrophil chemoattractants, such as CXCL8 (IL-8), we examined the effect of secukinumab on neutrophil function in PsA. METHODS: Nineteen patients with active PsA were treated with secukinumab. Clinical response [PsA Response Criteria (PsARC) and Psoriasis Area and Severity Index (PASI)] and peripheral blood neutrophil function (apoptosis, receptor expression, phagocytosis/killing, chemotaxis and RNA expression) were measured at 12 week intervals for 48 weeks and compared with age- and sex-matched healthy controls. RESULTS: At 12 weeks, 12/16 (75%) patients had a PsARC response (100% at 36 weeks) and 10/14 (71%) achieved a 90% PASI response. At baseline, there were no differences in PsA neutrophil reactive oxygen species generation, constitutive or cytokine-delayed apoptosis, chemotaxis or phagocytosis of opsonized Staphylococcus aureus compared with healthy controls. Similarly, there were no differences in these functions from baseline to 12 weeks of therapy. However, surface levels of CD11b/CD18 and CD63 increased and expression of CD16 decreased during therapy. In addition, in a subgroup of early (12 week) responders to secukinumab, RNA sequencing revealed transcriptome changes predicting down-regulation of cytokine signalling and chemotaxis pathways and up-regulation of de novo gene expression pathways, including translation initiation, mRNA catabolism and translation. CONCLUSION: Complex changes in the properties of circulating neutrophils occur with secukinumab treatment in PsA that may indicate altered responsiveness to changes in both local and systemic levels of pro-inflammatory cytokines. However, host defence processes of neutrophils were unaltered.

Markers of immune dysregulation in response to the ageing gut: insights from aged murine gut microbiota transplants.

BACKGROUND: Perturbations in the composition and diversity of the gut microbiota are accompanied by a decline in immune homeostasis during ageing, characterized by chronic low-grade inflammation and enhanced innate immunity. Genetic insights into the interaction between age-related alterations in the gut microbiota and immune function remain largely unexplored. METHODS: We investigated publicly available transcriptomic gut profiles of young germ-free mouse hosts transplanted with old donor gut microbiota to identify immune-associated differentially expressed genes (DEGs). Literature screening of the Gene Expression Omnibus and PubMed identified one murine (Mus musculus) gene expression dataset (GSE130026) that included small intestine tissues from young (5-6 weeks old) germ-free mice hosts that were compared following 8 weeks after transplantation with either old (~ 24-month old; n = 5) or young (5-6 weeks old; n = 4) mouse donor gut microbiota. RESULTS: A total of 112 differentially expressed genes (DEGs) were identified and used to construct a gut network of encoded proteins, in which DEGs were functionally annotated as being involved in an immune process based on gene ontology. The association between the expression of immune-process DEGs and abundance of immune infiltrates from gene signatures in normal colorectal tissues was estimated from The Cancer Genome Atlas (TCGA) and Genotype-Tissue Expression (GTEx) project. The analysis revealed a 25-gene signature of immune-associated DEGs and their expression profile was positively correlated with naïve T-cell, effector memory T-cell, central memory T-cell, resident memory T-cell, exhausted T-cell, resting Treg T-cell, effector Treg T-cell and Th1-like colorectal gene signatures. Conclusions These genes may have a potential role as candidate markers of immune dysregulation during gut microbiota ageing. Moreover, these DEGs may provide insights into the altered immune response to microbiota in the ageing gut, including reduced antigen presentation and alterations in cytokine and chemokine production.

Anti-Inflammatory Effects and Decreased Formation of Neutrophil Extracellular Traps by Enoxaparin in COVID-19 Patients.

Neutrophil Extracellular Traps (NETs) are a contributing factor of vascular thrombosis and alveolar damage in COVID-19 patients. As enoxaparin is currently used to inhibit vascular thrombosis, this study aimed to investigate whether enoxaparin also reduced inflammation and NETs in COVID-19 patients. Patients with COVID-19 infection were classified into three groups: mild, moderate, and severe (n = 10 for all groups). Plasma was collected from patients and healthy donors (n = 10). Neutrophils isolated from healthy controls were incubated with COVID-19 or healthy plasma, and with or without enoxaparin pretreatment in vitro. Neutrophils and plasma isolated from patients treated with enoxaparin were also investigated. The levels of inflammatory cytokines and NET products such as dsDNA, NE, MPO−DNA and Histone−DNA complexes in plasma and supernatants were measured using immunofluorescence staining and ELISA kits. The expression of inflammatory signaling genes by neutrophils (RELA, SYK, ERK and PKC) was measured using real-time qPCR. The levels of NET products were elevated in the plasma of COVID-19 patients, particularly in the severe group (p < 0.01). Moreover, plasma from the severe group enhanced NET formation (p < 0.01) from neutrophils in vitro. Enoxaparin pretreatment in vitro decreased plasma-induced NETs in a dose-dependent manner and down-regulated the expression of inflammatory genes (p < 0.05). Patients treated with prophylactic enoxaparin showed lower inflammatory cytokine levels and expression of inflammatory genes (p < 0.05). Increased NETs were associated with the severity of COVID-19 infection, particularly in patients with severe pneumonia, and could be used as biomarkers to assess disease severity. Enoxaparin pretreatment inhibited NETs and reduced the expression of inflammatory cytokines, and these effects mostly persisted in patients treated with prophylactic enoxaparin.

Internalization of Neutrophil-Derived Microvesicles Modulates TNFα-Stimulated Proinflammatory Cytokine Production in Human Fibroblast-Like Synoviocytes.

Neutrophil-derived microvesicles (NDMVs) have the potential to exert anti-inflammatory effects. Our study aimed to explore the effects of NDMVs on proinflammatory cytokines expressed by tumor necrosis factor α (TNFα)-stimulated fibroblast-like synoviocytes (FLS). FLS were isolated from the synovium of knee osteoarthritis (OA) patients undergoing surgery. NDMVs, isolated from TNFα-stimulated healthy neutrophils, were characterized by electron microscopy and nanoparticle tracking analysis. MTT and scratch wound healing assays were used to measure FLS viability and migration after treatment with NDMVs, while internalization of fluorescently labeled NDMVs was appraised by flow cytometry and confocal microscopy. Levels of proinflammatory cytokines in supernatants were quantified by the Bio-Plex system. Incubation of FLS with NDMVs at a vesicle/cell ratio of 100 resulted in a time-dependent uptake, with 35% of synoviocytes containing microvesicles over a 6-24 h time period, with no significant change in cell viability. TNFα stimulated the cytokine expression in FLS, and NDMVs down-regulated TNFα-induced expression of IL-5, IL-6, IL-8, MCP-1, IFNγ and MIP-1ß. However, this down-regulation was selective, as NDMVs had no significant effects on TNFα-stimulated expression of IL-2 or IL-4. NDMVs were internalized by FLS to inhibit TNFα-stimulated broad-spectrum proinflammatory cytokine secretion. NDMVs, therefore, may exhibit an anti-inflammatory role in the regulation of the FLS function.

The clinical significance of antinuclear antibodies and specific autoantibodies in juvenile and adult systemic lupus erythematosus patients.

BACKGROUND: Juvenile systemic lupus erythematosus (JSLE) and adult SLE (ASLE) patients present with different clinical manifestations, but it is unknown if there are differences in their antinuclear autoantibody (ANA) profiles or if staining patterns are associated with specific autoantibodies and clinical manifestations. OBJECTIVE: To determine whether distinct types and numbers of ANA-staining patterns are associated with specific autoantibodies and clinical manifestations in JSLE and ASLE patients. METHODS: A retrospective study was performed in Thai children (n = 146) and adults (n = 180) diagnosed with SLE using the Systemic Lupus International Collaborating Clinics classification criteria. RESULTS: JSLE patients with a homogeneous pattern of staining and anti-dsDNA or anti-nucleosome antibodies in serum, developed renal involvement, leukopenia and acute/subacute cutaneous LE. Coarse speckled pattern with anti-RNP or anti-Sm showed thrombocytopenia and renal involvement in JSLE patients, but leukopenia in both groups. JSLE patients with fine-coarse speckled pattern and anti-RNP, anti-Sm, anti-Ro-52 or anti-SSA developed leukopenia, thrombocytopenia and renal involvement, whilst hemolytic anemia and serositis were commonly found in those with anti-Ro-52. Median SLEDAI score was higher in JSLE than ASLE patients. CONCLUSIONS: Detailed ANA-staining patterns with specific autoantibodies show particular clinical manifestations and hence prompt further clinical investigations in both JSLE and ASLE patients. Therefore, this study demonstrates that distinct patterns of ANA staining and specific autoantibodies are clinically important in both children and adults with SLE.

Autoantibodies to neutrophil extracellular traps represent a potential serological biomarker in rheumatoid arthritis.

Neutrophil extracellular traps (NETs) are networks of extracellular chromatin decorated with antimicrobial proteins, formed by neutrophils to entrap pathogens. NETs have been implicated in the generation of autoimmune reactions. Here, we investigate the reactivity of rheumatoid arthritis (RA) serum antibodies with NETs and explore whether anti-NET antibodies (ANETA) have a potential as biomarker in RA. To quantify ANETA, we developed an ELISA with NETs isolated from stimulated human neutrophils and verified the results by immunofluorescence staining of NETs. ANETA were detected in 22%-69% of RA sera. No significant differences were observed in the reactivity of RA sera with NETs originating from RA patients and healthy control neutrophils, nor with NETs induced by phorbol 12-myristate 13-acetate or the calcium ionophore A23187. ANETA were detected already at baseline in newly diagnosed RA patients and both increased and decreased levels were observed in samples with a median follow-up of 7 years. By ANETA ELISA, we showed that ANETA are also present in sera of patients with systemic lupus erythematosus (36%), Sjögren's syndrome (76%) and scleroderma (61%). In addition to antibodies to NETs, also the presence of NETs or NET fragments in RA sera was determined using a sandwich ELISA. Elevated levels of NETs or NET fragments were detected in 32% of the sera. To assess the potency of ANETA as a biomarker in RA, we compared ANETA positivity with other clinical features. The presence of ANETA was significantly higher in rheumatoid factor (RF)-positive patients, but did not correlate with anti-citrullinated protein antibodies (ACPA), nor with the presence of NET fragments in serum. In addition, no correlation was observed with age, gender, onset of the disease, disease activity and inflammatory markers. These findings suggest that ANETA may be an independent biomarker in RA and possibly also in other autoimmune diseases.

Human neutrophils in auto-immunity.

Human neutrophils have great capacity to cause tissue damage in inflammatory diseases via their inappropriate activation to release reactive oxygen species (ROS), proteases and other tissue-damaging molecules. Furthermore, activated neutrophils can release a wide variety of cytokines and chemokines that can regulate almost every element of the immune system. In addition to these important immuno-regulatory processes, activated neutrophils can also release, expose or generate neoepitopes that have the potential to break immune tolerance and result in the generation of autoantibodies, that characterise a number of human auto-immune diseases. For example, in vasculitis, anti-neutrophil cytoplasmic antibodies (ANCA) that are directed against proteinase 3 or myeloperoxidase are neutrophil-derived autoantigens and activated neutrophils are the main effector cells of vascular damage. In other auto-immune diseases, these neutrophil-derived neoepitopes may arise from a number of processes that include release of granule enzymes and ROS, changes in the properties of components of their plasma membrane as a result of activation or apoptosis, and via the release of Neutrophil Extracellular Traps (NETs). NETs are extracellular structures that contain chromatin that is decorated with granule enzymes (including citrullinated proteins) that can act as neo-epitopes to generate auto-immunity. This review therefore describes the processes that can result in neutrophil-mediated auto-immunity, and the role of neutrophils in the molecular pathologies of auto-immune diseases such as vasculitis, rheumatoid arthritis (RA) and systemic lupus erythematosus (SLE). We discuss the potential role of NETs in these processes and some of the debate in the literature regarding the role of this phenomenon in microbial killing, cell death and auto-immunity.

1H NMR Metabolomics Identifies Underlying Inflammatory Pathology in Osteoarthritis and Rheumatoid Arthritis Synovial Joints.

Despite osteoarthritis (OA) and rheumatoid arthritis (RA) being typically age-related, their underlying etiologies are markedly different. We used 1H nuclear magnetic resonance (NMR) spectroscopy to identify differences in metabolite profiles in low volumes of OA and RA synovial fluid (SF). SF was aspirated from knee joints of 10 OA and 14 RA patients. 100 µL SF was analyzed using a 700 MHz Avance IIIHD Bruker NMR spectrometer with a TCI cryoprobe. Spectra were analyzed by Chenomx, Bruker TopSpin and AMIX software. Statistical analysis was undertaken using Metaboanalyst. 50 metabolites were annotated, including amino acids, saccharides, nucleotides and soluble lipids. Discriminant analysis identified group separation between OA and RA cohorts, with 32 metabolites significantly different between OA and RA SF (false discovery rate (FDR) < 0.05). Metabolites of glycolysis and the tricarboxylic acid cycle were lower in RA compared to OA; these results concur with higher levels of inflammation, synovial proliferation and hypoxia found in RA compared to OA. Elevated taurine in OA may indicate increased subchondral bone sclerosis. We demonstrate that quantifiable differences in metabolite abundance can be measured in low volumes of SF by 1H NMR spectroscopy, which may be clinically useful to aid diagnosis and improve understanding of disease pathogenesis.

Neutrophil activation signature in juvenile idiopathic arthritis indicates the presence of low-density granulocytes.

Objective: JIA is an autoimmune, inflammatory disease with involvement of innate and adaptive immune responses. However, the role of neutrophils in JIA pathogenesis remains unclear. This study aimed to identify and validate neutrophil gene expression signatures in JIA using public microarray datasets and new clinical samples. Methods: Three suitable datasets were analysed by significance analysis of microarray and Ingenuity. Neutrophils and peripheral blood mononuclear cells (PBMCs) were isolated from a new cohort of JIA patients and healthy paediatric controls (HCs). Gene expression was validated using quantitative PCR. Serum concentrations of proteins were measured using ELISA. Low-density granulocytes (LDGs) in JIA and HC PBMCs were quantified by flow cytometry using forward/side-scatter properties. Results: Ingenuity identified transcriptional regulation (false discovery rate < 0.05) by G-CSF, GM-CSF and IL-8 along with expression of neutrophil granule protein genes including ELANE, MPO, MMP8 and MMP9 in datasets from JIA PBMCs. LDG counts were elevated in JIA compared with HCs (2.5% vs 1.4%; P = 0.007). Transcripts for MMP8 (P = 0.005), MPO (P = 0.0124) and Fcγ Receptor 1B (FCγR1B) (P = 0.0417) were significantly higher in JIA compared with HC neutrophils. MMP9 protein levels were lower in systemic JIA patient sera [355.95 ng/ml (s.d. 250.03)] compared with HCs [675.41 ng/ml (s.d. 181.17); P = 0.007], but levels of elastase, MPO and MMP8 were not significantly different. Conclusion: LDGs are elevated in JIA and contribute to the transcriptomic profile of JIA PBMCs. JIA neutrophils express higher levels of MMP8 and FCGR1B, which may be implicated in disease pathology through the release of proteases and reactive oxygen metabolites, causing systemic inflammation and damage to joints.

Interferon gene expression signature in rheumatoid arthritis neutrophils correlates with a good response to TNFi therapy.

OBJECTIVE: The aim of this study was to use whole transcriptome sequencing (RNA-Seq) of RA neutrophils to identify pre-therapy gene expression signatures that correlate with disease activity or response to TNF inhibitor (TNFi) therapy. METHODS: Neutrophils were isolated from the venous blood of RA patients (n = 20) pre-TNFi therapy and from healthy controls (n = 6). RNA was poly(A) selected and sequenced on the Illumina HiSeq 2000 platform. Reads were mapped to the human genome (hg19) using TopHat and differential expression analysis was carried out using edgeR (5% false discovery rate). Signalling pathway analysis was carried out using Ingenuity Pathway Analysis (IPA) software. IFN signalling was confirmed by western blotting for phosphorylated signal transducer and activator of transcription (STAT) proteins. Response to TNFi was measured at 12 weeks using change in the 28-item DAS (DAS28). RESULTS: Pathway analysis with IPA predicted activation of IFN signalling in RA neutrophils, identifying 178 IFN-response genes regulated by IFN-α, IFN-ß or IFN-γ (P < 0.01). IPA also predicted activation of STAT1, STAT2 and STAT3 transcription factors in RA neutrophils (P < 0.01), which was confirmed by western blotting. Expression of IFN-response genes was heterogeneous and patients could be categorized as IFN-high or IFN-low. Patients in the IFN-high group achieved a better response to TNFi therapy [ΔDAS28, P = 0.05, odds ratio (OR) 1.4 (95% CI 1.005, 1.950)] than patients in the IFN-low group. The level of expression of IFN-response genes (IFN score) predicted a good response [European League Against Rheumatism (EULAR) criteria] to TNFi using receiver operating characteristic curve analysis (area under the curve 0.76). CONCLUSION: IFN-response genes are significantly up-regulated in RA neutrophils compared with healthy controls. Higher IFN-response gene expression in RA neutrophils correlates with a good response to TNFi therapy.

Effects of IL-6 and IL-6 blockade on neutrophil function in vitro and in vivo.

OBJECTIVES: Reports on the regulation of neutrophil function by IL-6 are often conflicting. Therapeutic inhibition of IL-6 in RA is associated with occasional neutropenia, but the mechanisms underlying this observation are poorly understood. This study investigated interactions between IL-6, the anti-IL-6 receptor agent tocilizumab (TCZ) and neutrophils in vitro and in vivo. METHODS: Neutrophils were isolated from healthy controls and incubated in vitro with pharmacologically relevant concentrations of IL-6 or TCZ. Neutrophils were also isolated from RA patients, including a cohort following TCZ therapy. Apoptosis was measured by annexin V/propidium iodide (PI) flow cytometry; phagocytosis was measured by incubating apoptotic neutrophils with THP-1-derived macrophages; chemotaxis was measured using cell migration through hanging-cell inserts towards IL-8 and cell surface proteins, including adhesion molecules CD11b (αMß2 integrin) and CD62L (L-selectin) were measured by flow cytometry. RESULTS: IL-6 (10-100 ng/ml) did not affect the rate of neutrophil apoptosis, priming of the respiratory burst or adhesion molecule expression nor act as a neutrophil chemoattractant. However, IL-6 enhanced signal transducer and activator of transcription 3 (STAT3) activation and neutrophil migration towards IL-8. TCZ in vitro did not induce apoptosis or phagocytosis of neutrophils, nor did it have a significant effect upon apoptosis or cell surface molecule expression. Neutrophil functions in ex vivo neutrophils from RA patients receiving TCZ treatment were unaffected. CONCLUSION: Therapeutic blockade of IL-6, while inducing a transient neutropenia, does not directly affect neutrophil functions associated with host defence. TCZ-associated neutropenia cannot be explained by direct induction of apoptosis by TCZ, induction of apoptosis following depletion of IL-6, nor increased phagocytosis of neutrophils.

New insights into healthy ageing, inflammageing and frailty using metabolomics.

Human ageing is a normal process and does not necessarily result in the development of frailty. A mix of genetic, environmental, dietary, and lifestyle factors can have an impact on ageing, and whether an individual develops frailty. Frailty is defined as the loss of physiological reserve both at the physical and cellular levels, where systemic processes such as oxidative stress and inflammation contribute to physical decline. The newest "omics" technology and systems biology discipline, metabolomics, enables thorough characterisation of small-molecule metabolites in biological systems at a particular time and condition. In a biological system, metabolites-cellular intermediate products of metabolic reactions-reflect the system's final response to genomic, transcriptomic, proteomic, epigenetic, or environmental alterations. As a relatively newer technique to characterise metabolites and biomarkers in ageing and illness, metabolomics has gained popularity and has a wide range of applications. We will give a comprehensive summary of what is currently known about metabolomics in studies of ageing, with a focus on biomarkers for frailty. Metabolites related to amino acids, lipids, carbohydrates, and redox metabolism may function as biomarkers of ageing and/or frailty development, based on data obtained from human studies. However, there is a complexity that underpins biological ageing, due to both genetic and environmental factors that play a role in orchestrating the ageing process. Therefore, there is a critical need to identify pathways that contribute to functional decline in people with frailty.

Regulation of dermal fibroblasts by human neutrophil peptides.

Human neutrophil peptides (HNPs) can induce cell proliferation and activation so their growth promoting activities may have potential clinical benefit. This study investigated the effects of HNPs on human dermal fibroblasts. Differential gene expression in HNP-treated cells and genes involved in regulating intracellular pathways were explored. Dermal fibroblasts were isolated from healthy neonatal foreskin and treated with HNPs in 2D and 3D cell culture systems. The expression of cell proliferation (Ki-67) gene and cell activation (COL1A1) gene plus their proteins was measured. Differential gene expression was determined using RNA-seq, and upregulated and downregulated genes were mapped onto intracellular pathways by KEGG analysis and Gene Ontology databases. HNPs significantly increased cell proliferation without cytotoxicity whilst HNP1 enhanced expression of COL1A1 and type I collagen production in 2D cells and 3D spheroids. RNA-sequencing analysis showed gene clustering with clear separation between HNP1-treated and control groups. A heatmap of top 50 differentially expressed genes was consistent among HNP1-treated samples. Most upregulated genes were associated with cell proliferation and activation as mapped into intracellular pathways whilst most downregulated genes belonged to steroid/arachidonic acid metabolism and inflammatory signaling pathways. HNP1 increased cell proliferation and activation but reduced lipid metabolism and inflammation.

miRNA-132-5p mediates a negative feedback regulation of IL-8 secretion through S100A8/A9 downregulation in neutrophil-like HL-60 cells.

Background: Neutrophils are an important source of pro-inflammatory and immunomodulatory cytokines. This makes neutrophils efficient drivers of interactions with immune and non-immune cells to maintain homeostasis and modulate the inflammatory process by notably regulating the release of cytokines. Ca2+-dependent regulatory mechanism encompassing cytokine secretion by neutrophils are not still identified. In this context, we propose to define new insights on the role of Ca2+-binding proteins S100A8/A9 and on the regulatory role of miRNA-132-5p, which was identified as a regulator of S100A8/A9 expression, on IL-8 secretion. Methods: Differentiated HL-60 cells, a human promyelocytic leukemia cell line that can be induced to differentiate into neutrophil-like cells, were used as a model of human neutrophils and treated with N- formyl-methionyl-leucyl-phenylalanine (fMLF), a bacterial peptide that activates neutrophils. shRNA knockdown was used to define the role of selected targets (S100A8/A9 and miRNA-132-5p) on IL-8 secretion. Results and discussion: Different types of cytokines engage different signaling pathways in the secretion process. IL-8 release is tightly regulated by Ca2+ binding proteins S100A8/A9. miRNA-132-5p is up-regulated over time upon fMLF stimulation and decreases S100A8/A9 expression and IL-8 secretion. Conclusion: These findings reveal a novel regulatory loop involving S100A8/A9 and miRNA-132-5p that modulates IL-8 secretion by neutrophils in inflammatory conditions. This loop could be a potential target for therapeutic intervention in inflammatory diseases.

Analysis of SF and plasma cytokines provides insights into the mechanisms of inflammatory arthritis and may predict response to therapy.

OBJECTIVES: Biologic drugs have revolutionized the care of RA, but are expensive and not universally effective. To further understand the inflammatory mechanisms underlying RA and identify potential biomarkers predicting response to therapy, we measured multiple cytokine concentrations in SF of patients with inflammatory arthritides (IAs) and, in a subset of patients with RA, correlated this with response to TNF-α inhibition. METHODS: SF from 42 RA patients and 19 non-RA IA patients were analysed for 12 cytokines using a multiplex cytokine assay. Cytokines were also measured in the plasma of 16 RA patients before and following treatment with anti-TNF-α. Data were analysed using Mann-Whitney U-test, Spearman's rank correlation and cluster analysis with the Kruskal-Wallis test with Dunn's post-test analysis. RESULTS: RA SF contained significantly elevated levels of IL-1ß, IL-1ra, IL-2, IL-4, IL-8, IL-10, IL-17, IFN-γ, G-CSF, GM-CSF and TNF-α compared with other IA SF. RA patients who did not respond to anti-TNF therapy had elevated IL-6 in their SF pre-therapy (P < 0.05), whereas responders had elevated IL-2 and G-CSF (P < 0.05). Plasma cytokine concentrations were not significantly modulated by TNF inhibitors, with the exception of IL-6, which decreased after 12 weeks (P < 0.05). CONCLUSIONS: Cytokine profiles in RA SF vary with treatment and response to therapy. Cytokine concentrations are significantly lower in plasma than in SF and relatively unchanged by TNF inhibitor therapy. Concentrations of IL-6, IL-2 and G-CSF in SF may predict response to TNF inhibitors.

Matrix metalloproteinase-13 is fully activated by neutrophil elastase and inactivates its serpin inhibitor, alpha-1 antitrypsin: Implications for osteoarthritis.

Matrix metalloproteinase-13 (MMP-13) is a uniquely important collagenase that promotes the irreversible destruction of cartilage collagen in osteoarthritis (OA). Collagenase activation is a key control point for cartilage breakdown to occur, yet our understanding of the proteinases involved in this process is limited. Neutrophil elastase (NE) is a well-described proteoglycan-degrading enzyme which is historically associated with inflammatory arthritis, but more recent evidence suggests a potential role in OA. In this study, we investigated the effect of neutrophil elastase on OA cartilage collagen destruction and collagenase activation. Neutrophil elastase induced significant collagen destruction from human OA cartilage ex vivo, in an MMP-dependent manner. In vitro, neutrophil elastase directly and robustly activated pro-MMP-13, and N-terminal sequencing identified cleavage close to the cysteine switch at 72 MKKPR, ultimately resulting in the fully active form with the neo-N terminus of 85 YNVFP. Mole-per-mole, activation was more potent than by MMP-3, a classical collagenase activator. Elastase was detectable in human OA synovial fluid and OA synovia which displayed histologically graded evidence of synovitis. Bioinformatic analyses demonstrated that, compared with other tissues, control cartilage exhibited remarkably high transcript levels of the major elastase inhibitor, (AAT) alpha-1 antitrypsin (gene name SERPINA1), but these were reduced in OA. AAT was located predominantly in superficial cartilage zones, and staining enhanced in regions of cartilage damage. Finally, active MMP-13 specifically inactivated AAT by removal of the serine proteinase cleavage/inhibition site. Taken together, this study identifies elastase as a novel activator of pro-MMP-13 that has relevance for cartilage collagen destruction in OA patients with synovitis.