The CC chemokines CCL8, CCL13 and CCL20 are local inflammatory biomarkers of HLA-B27-associated uveitis.

PURPOSE: To determine the concentrations of the CC chemokines CCL2, CCL7, CCL8, CCL11, CCL13, CCL20, CCL24 and CCL26 in aqueous humour (AH) samples from patients with specific uveitic entities. METHODS: Aqueous humour samples from patients with active uveitis associated with Behçet's disease (BD) (n = 13), sarcoidosis (n = 8), HLA-B27-related inflammation (n = 12), Vogt-Koyanagi-Harada (VKH) disease (n = 12) and control patients (n = 9) were assayed with the use of a multiplex assay. RESULTS: When considering all uveitis patients as one group, all chemokine levels except CCL2 were significantly increased compared to controls. CCL8, CCL13 and CCL20 were the most strongly upregulated, 48-fold, 118-fold and 173-fold, respectively, above control AH levels. CCL8 and CCL13 levels were significantly higher in HLA-B27-associated uveitis than in sarcoidosis and VKH disease. CCL20 levels were significantly higher in HLA-B27-associated uveitis than in BD, sarcoidosis and VKH disease. In addition, CCL20 levels were significantly higher in BD than in VKH disease. In HLA-B27-associated uveitis, CCL8, CCL13 and CCL20 were upregulated 111-fold, 255-fold and 465-fold, respectively, compared with controls. CCL8, CCL13 and CCL20 levels were significantly higher in nongranulomatous uveitis (BD and HLA-B27-associated uveitis) than in granulomatous uveitis (sarcoidosis and VKH disease). CONCLUSION: Immune responses mediated by CCL8, CCL13 and CCL20 appear to be more potent in nongranulomatous uveitis, particularly in HLA-B27-associated uveitis.

Dynamics of Colon Monocyte and Macrophage Activation During Colitis.

Background: Macrophages are pivotal in coordinating a range of important processes in the intestines, including controlling intracellular infections and limiting damaging inflammation against the microbiota. However, it is not clear how gut macrophages, relative to recruited blood monocytes and other myeloid cells, contribute to the intestinal inflammatory milieu, nor how macrophages and their monocyte precursors mediate recruitment of other immune cells to the inflamed intestine. Methods: Myeloid cell populations isolated from colonic inflammatory bowel disease (IBD) or murine dextran sulphate sodium (DSS) induced colitis were assessed using flow cytometry and compared to healthy controls. In addition, mRNA expression profiles in human and murine colon samples, and in macrophages and monocytes from healthy and inflamed murine colons, were analysed by quantitative PCR (qPCR) and mRNA microarray. Results: We show that the monocyte:macrophage balance is disrupted in colon inflammation to favour recruitment of CD14+HLA-DRInt cells in humans, and Ly6CHi monocytes in mice. In addition, we identify that murine blood monocytes receive systemic signals enabling increased release of IL-1ß prior to egress from the blood into the colon. Further, once within the colon and relative to other myeloid cells, monocytes represent the dominant local source of both IL-1ß and TNF. Finally, our data reveal that, independent of inflammation, murine colon macrophages act as a major source of Ccl7 and Ccl8 chemokines that trigger further recruitment of their pro-inflammatory monocyte precursors. Conclusions: Our work suggests that strategies targeting macrophage-mediated monocyte recruitment may represent a promising approach for limiting the chronic inflammation that characterises IBD.

MicroRNA-146a-5p attenuates visceral hypersensitivity through targeting chemokine CCL8 in the spinal cord in a mouse model of colitis.

Visceral pain, observed in inflammatory bowel disease (IBD) patients, is a challenging medical problem and remains poorly understood because the mechanisms underlying it are unclear. Emerging evidence indicates that microRNAs (miRNAs) play a crucial role in the pathogenesis of acute and chronic pain. In this study, we aimed to explore the potential role of miR-146a-5p (the mature form of miR-146a) in a mouse model of colitis induced by intracolonic injection of trinitrobenzene sulfonic acid (TNBS). We found that induction of colitis resulted in visceral hyperalgesia manifested by a decreased pain threshold to colorectal distension and upregulation of miR-146a-5p expression in the lumbosacral spinal cord. In situ hybridization and immunohistochemistry results showed that miR-146a-5p was colocalized with neuronal marker NeuN, but not with astrocytic marker GFAP or microglial marker IBA-1. Dual-luciferase reporter assay showed that miR-146a-5p directly targeted the 3'-untranslated region (UTR) of CCL8, which was previously identified as an important regulator of visceral pain. In cultured Neuro-2a cells, TNF-α-induced CCL8 upregulation was decreased by transfection of miR-146a-5p mimic dose-dependently. In vivo, exogenous supplementation of miR-146a-5p by intrathecal miR-146a-5p agomir significantly alleviated visceral pain and decreased CCL8 expression in colitis mice. Furthermore, inhibition of CCL8 expression by CCL8 siRNA relieved colitis-induced visceral nociception. Finally, in naïve mice intrathecal miR-146a-5p antagomir upregulated CCL8 expression and induced visceral pain hypersensitivity, which could be partially rescued by neutralization of CCL8. Taken together, the present findings indicate that miR-146a-5p may be an endogenous suppressor of visceral pain and exogenous supplementation of miR-146a-5p could exert an analgesic effect at least partly by targeting spinal CCL8 expression. Thus, miR-146a-5p may serve as a novel therapeutic target for visceral pain intervention in the context of colitis.

MicroRNA-124 alleviates chronic skin inflammation in atopic eczema via suppressing innate immune responses in keratinocytes.

Chronic skin inflammation in atopic eczema is associated with elevated expression of proinflammatory genes and activation of innate immune responses in keratinocytes. MicroRNAs (miRNAs) are short, single-stranded RNA molecules that silence genes via the degradation of target mRNAs or inhibition of translation. Recent studies have demonstrated that miR-124 is associated with regulation of inflammation factors in several diseases. The aim of this study was to investigate the role of miR-124 in skin inflammation of atopic eczema. We showed that miR-124 expression is decreased in chronic lesional skin of patients with atopic eczema, and could be strongly inhibited by IFN-γ and TNF-α. Through Western blot, real-time PCR and luciferase assays, we revealed that miR-124 inhibited the expression of p65, a member of NF-κB family which can regulate many factors involved in the immune response and inflammatory reactions, through direct targeting. Further, upon IFN-γ or TNF-α stimulation, IL8, CCL5 and CCL8 showed to be significantly upregulated by IFN-γ or TNF-α, downregulated by miR-124; the promotive effect of IFN-γ and TNF-α could be partially reversed by miR-124. The levels of IL8, CCL5 and CCL8 could be significantly downregulated by p65 knockdown, upregulated by miR-124 inhibition; the suppressive effect of p65 knockdown could be partially reversed by miR-124. Moreover, contrary to miR-124, p65, IL8, CCL5 and CCL8 mRNA expression was upregulated in chronic lesional skin of patients with atopic eczema, and all inversely correlated with miR-124. Taken together, our data demonstrate that miR-124 controls NF-κB-dependent inflammatory responses in keratinocytes and chronic skin inflammation in atopic eczema; rescuing miR-124 expression presents a promising strategy for atopic eczema treatment.

Cutting Edge: Origins, Recruitment, and Regulation of CD11c+ Cells in Inflamed Islets of Autoimmune Diabetes Mice.

In NOD mice, CD11c+ cells increase greatly with islet inflammation and contribute to autoimmune destruction of pancreatic ß cells. In this study, we investigated their origin and mechanism of recruitment. CD11c+ cells in inflamed islets resembled classical dendritic cells based on their transcriptional profile. However, the majority of these cells were not from the Zbtb46-dependent dendritic-cell lineage. Instead, monocyte precursors could give rise to CD11c+ cells in inflamed islets. Chemokines Ccl5 and Ccl8 were persistently elevated in inflamed islets and the influx of CD11c+ cells was partially dependent on their receptor Ccr5. Treatment with islet Ag-specific regulatory T cells led to a marked decrease of Ccl5 and Ccl8, and a reduction of monocyte recruitment. These results implicate a monocytic origin of CD11c+ cells in inflamed islets and suggest that therapeutic regulatory T cells directly or indirectly regulate their influx by altering the chemotactic milieu in the islets.

Outside-in? Acute fetal systemic inflammation in very preterm chronically catheterized sheep fetuses is not driven by cells in the fetal blood.

BACKGROUND: The preterm birth syndrome (delivery before 37 weeks gestation) is a major contributor to the global burden of perinatal morbidity and death. The cause of preterm birth is complex, multifactorial, and likely dependent, at least in part, on the gestational age of the fetus. Intrauterine infection is frequent in preterm deliveries that occur at <32 weeks gestation; understanding how the fetus responds to proinflammatory insult will be an important step towards early preterm birth prevention. However, animal studies of infection and inflammation in prematurity commonly use older fetuses that possess comparatively mature immune systems. OBJECTIVE: Aiming to characterize acute fetal responses to microbial agonist at a clinically relevant gestation, we used 92-day-old fetuses (62% of term) to develop a chronically catheterized sheep model of very preterm pregnancy. We hypothesized that any acute fetal systemic inflammatory responses would be driven by signaling from the tissues exposed to Escherichia coli lipopolysaccharide that is introduced into the amniotic fluid. STUDY DESIGN: Eighteen ewes that were carrying a single fetus at 92 days of gestation had recovery surgery to place fetal tracheal, jugular, and intraamniotic catheters. Animals were recovered for 24 hours before being administered either intraamniotic E coli lipopolysaccharide (n = 9) or sterile saline solution (n = 9). Samples were collected for 48 hours before euthanasia and necroscopy. Fetal inflammatory responses were characterized by microarray analysis, quantitative polymerase chain reaction, and enzyme-linked immunosorbent assay. RESULTS: Intraamniotic lipopolysaccharide reached the distal trachea within 2 hours. Lipopolysaccharide increased tracheal fluid interleukin-8 within 2 hours and generated a robust inflammatory response that was characterized by interleukin-6 signaling pathway activation and up-regulation of cell proliferation but no increases in inflammatory mediator expression in cord blood RNA. CONCLUSIONS: In very preterm sheep fetuses, lipopolysaccharide stimulates inflammation in the fetal lung and fetal skin and stimulates a systemic inflammatory response that is not generated by fetal blood cells. These data argue for amniotic fluid-exposed tissues that play a key role in driving acute fetal and intrauterine inflammatory responses.

PpiA antigen specific immune response is a potential biomarker for latent tuberculosis infection.

One third of the world's population is estimated to harbour latent tuberculosis infection (LTBI). Around 10% of them have the life time risk of developing active tuberculosis (PTB). Currently there is no gold standard test for identifying LTBI. Therefore identification of specific markers for LTBI will help as to develop a test specific for LTBI. Earlier, in our immunoproteomic analysis, we found that peptidyl-prolyl cis-trans isomerase A (PpiA) protein-containing fractions induced significantly higher interferon-gamma (IFN-γ) response in LTBI than in PTB. Immunological characterisation of recombinant PpiA protein was carried out in the current study. We have studied 10 cytokines and 2 chemokine responses against PpiA and standard antigens such as early secretory antigenic target-6 (ESAT-6) and culture filtrate antigen-10 (CFP-10). In healthy household contacts (HHC), all the tested antigens induced significantly higher levels of IFN-γ and Interlukin-8 (IL-8) compared with those in PTB. PpiA-specific IL-12p40 response was significantly increased in HHC compared with that in PTB. PpiA antigen-specific IFN-γ and IL-12p40 both showed 86% positivity in HHC, whereas in PTB, they showed 20% and 38% positivity, respectively. In terms of IFN-γ/TNF-α ratio, PpiA displayed 86% (30/35) positivity in HHC and 18% (7/39) positivity in PTB. In summary we found that PpiA-specific IFN-γ and IFN-γ/TNF-α ratio response were specific biomarkers for LTBI identification.

Allergic airway inflammation decreases lung bacterial burden following acute Klebsiella pneumoniae infection in a neutrophil- and CCL8-dependent manner.

The Th17 cytokines interleukin-17A (IL-17A), IL-17F, and IL-22 are critical for the lung immune response to a variety of bacterial pathogens, including Klebsiella pneumoniae. Th2 cytokine expression in the airways is a characteristic feature of asthma and allergic airway inflammation. The Th2 cytokines IL-4 and IL-13 diminish ex vivo and in vivo IL-17A protein expression by Th17 cells. To determine the effect of IL-4 and IL-13 on IL-17-dependent lung immune responses to acute bacterial infection, we developed a combined model in which allergic airway inflammation and lung IL-4 and IL-13 expression were induced by ovalbumin sensitization and challenge prior to acute lung infection with K. pneumoniae. We hypothesized that preexisting allergic airway inflammation decreases lung IL-17A expression and airway neutrophil recruitment in response to acute K. pneumoniae infection and thereby increases the lung K. pneumoniae burden. As hypothesized, we found that allergic airway inflammation decreased the number of K. pneumoniae-induced airway neutrophils and lung IL-17A, IL-17F, and IL-22 expression. Despite the marked reduction in postinfection airway neutrophilia and lung expression of Th17 cytokines, allergic airway inflammation significantly decreased the lung K. pneumoniae burden and postinfection mortality. We showed that the decreased lung K. pneumoniae burden was independent of IL-4, IL-5, and IL-17A and partially dependent on IL-13 and STAT6. Additionally, we demonstrated that the decreased lung K. pneumoniae burden associated with allergic airway inflammation was both neutrophil and CCL8 dependent. These findings suggest a novel role for CCL8 in lung antibacterial immunity against K. pneumoniae and suggest new mechanisms of orchestrating lung antibacterial immunity.

The transcriptional repressor BLIMP1 curbs host defenses by suppressing expression of the chemokine CCL8.

The transcriptional repressor B lymphocyte-induced maturation protein 1 (BLIMP1) is a master regulator of B and T cell differentiation. To examine the role of BLIMP1 in innate immunity, we used a conditional knockout (CKO) of Blimp1 in myeloid cells and found that Blimp1 CKO mice were protected from lethal infection induced by Listeria monocytogenes. Transcriptome analysis of Blimp1 CKO macrophages identified the murine chemokine (C-C motif) ligand 8, CCL8, as a direct target of Blimp1-mediated transcriptional repression in these cells. BLIMP1-deficient macrophages expressed elevated levels of Ccl8, and consequently Blimp1 CKO mice had higher levels of circulating CCL8, resulting in increased neutrophils in the peripheral blood, promoting a more aggressive antibacterial response. Mice lacking the Ccl8 gene were more susceptible to L. monocytogenes infection than were wild-type mice. Although CCL8 failed to recruit neutrophils directly, it was chemotactic for γ/δ T cells, and CCL8-responsive γ/δ T cells were enriched for IL-17F. Finally, CCL8-mediated enhanced clearance of L. monocytogenes was dependent on γ/δ T cells. Collectively, these data reveal an important role for BLIMP1 in modulating host defenses by suppressing expression of the chemokine CCL8.

Mechanisms of IFN-γ-induced apoptosis of human skin keratinocytes in patients with atopic dermatitis.

BACKGROUND: Enhanced apoptosis of keratinocytes is the main cause of eczema and spongiosis in patients with the common inflammatory skin disease atopic dermatitis (AD). OBJECTIVE: The aim of the study was to investigate molecular mechanisms of AD-related apoptosis of keratinocytes. METHODS: Primary keratinocytes isolated from patients with AD and healthy donors were used to study apoptosis by using annexin V/7-aminoactinomycin D staining. Illumina mRNA Expression BeadChips, quantitative RT-PCR, and immunofluorescence were used to study gene expression. In silico analysis of candidate genes was performed on genome-wide single nucleotide polymorphism data. RESULTS: We demonstrate that keratinocytes of patients with AD exhibit increased IFN-γ-induced apoptosis compared with keratinocytes from healthy subjects. Further mRNA expression analyses revealed differential expression of apoptosis-related genes in AD keratinocytes and skin and the upregulation of immune system-related genes in skin biopsy specimens of chronic AD lesions. Three apoptosis-related genes (NOD2, DUSP1, and ADM) and 8 genes overexpressed in AD skin lesions (CCDC109B, CCL5, CCL8, IFI35, LYN, RAB31, IFITM1, and IFITM2) were induced by IFN-γ in primary keratinocytes. The protein expression of IFITM1, CCL5, and CCL8 was verified in AD skin. In line with the functional studies and AD-related mRNA expression changes, in silico analysis of genome-wide single nucleotide polymorphism data revealed evidence of an association between AD and genetic markers close to or within the IFITM cluster or RAB31, DUSP1, and ADM genes. CONCLUSION: Our results demonstrate increased IFN-γ responses in skin of patients with AD and suggest involvement of multiple new apoptosis- and inflammation-related factors in the development of AD.

Mouse CCL8, a CCR8 agonist, promotes atopic dermatitis by recruiting IL-5+ T(H)2 cells.

Mouse CCL8 is a CC chemokine of the monocyte chemoattractant protein (MCP) family whose biological activity and receptor usage have remained elusive. Here we show that CCL8 is highly expressed in the skin, where it serves as an agonist for the chemokine receptor CCR8 but not for CCR2. This distinguishes CCL8 from all other MCP chemokines. CCL8 responsiveness defined a population of highly differentiated, CCR8-expressing inflammatory T helper type 2 (T(H)2) cells enriched for interleukin (IL)-5. Ccr8- and Ccl8-deficient mice had markedly less eosinophilic inflammation than wild-type or Ccr4-deficient mice in a model of chronic atopic dermatitis. Adoptive transfer studies established CCR8 as a key regulator of T(H)2 cell recruitment into allergen-inflamed skin. In humans, CCR8 expression also defined an IL-5-enriched T(H)2 cell subset. The CCL8-CCR8 chemokine axis is therefore a crucial regulator of T(H)2 cell homing that drives IL-5-mediated chronic allergic inflammation.

IFN-gamma, but not IP-10, MCP-2 or IL-2 response to RD1 selected peptides associates to active tuberculosis.

OBJECTIVES: To evaluate whether in vitro response to Mycobacterium tuberculosis RD1 peptides selected by computational analysis, measured by IFN-gamma, IP-10, MCP-2 or IL-2 production, is associated with active tuberculosis (TB) in a country with a high incidence of TB. METHODS: 129 individuals were prospectively enrolled, 41 with active-pulmonary TB and 88 without (household contacts and community controls). A whole blood assay based on RD1 selected peptides was performed. Soluble factors were evaluated by ELISA in plasma harvested at day1-post-culture. Enrolled individuals were also tested by QuantiFERON TB-Gold In tube (QFT-IT) and tuberculin skin tests (TST). RESULTS: IFN-gamma response to RD1 selected peptides was significantly higher in active TB patients than in household contacts and community controls. IP-10 and MCP-2 response did not differ between active TB patients and household contacts, although it was higher in these groups compared to community controls; conversely IL-2 response did not differ among the three groups. When IFN-gamma response to RD1 selected peptides was scored based on receiver-operator-characteristic analysis, active TB was predicted with 68% sensitivity and 86% specificity. QFT-IT and TST showed a sensitivity for active TB of 90% and 68% and a specificity of 58% and 59%, respectively. CONCLUSIONS: IFN-gamma (but not IP-10, MCP-2 and IL-2) response to RD1 selected peptides is associated with active TB with a higher specificity than QFT-IT and TST.

Synergistic up-regulation of MCP-2/CCL8 activity is counteracted by chemokine cleavage, limiting its inflammatory and anti-tumoral effects.

Chemokines mediate the inflammatory response by attracting various leukocyte types. MCP-2/CC chemokine ligand 8 (CCL8) was induced at only suboptimal levels in fibroblasts and endothelial cells by IL-1beta or IFN-gamma, unless these cytokines were combined. IFN-gamma also synergized with the TLR ligands peptidoglycan (TLR2), dsRNA (TLR3) or LPS (TLR4). Under these conditions, intact MCP-2/CCL8(1-76) produced by fibroblasts was found to be processed into MCP-2/CCL8(6-75), which lacked chemotactic activity for monocytic cells. Furthermore, the capacity of MCP-2/CCL8(6-75) to increase intracellular calcium levels through CCR1, CCR2, CCR3 and CCR5 was severely reduced. However, the truncated isoform still blocked these receptors for other ligands. MCP-2/CCL8(6-75) induced internalization of CCR2, inhibited MCP-1/CCL2 and MCP-2/CCL8 ERK signaling and antagonized the chemotactic activity of several CCR2 ligands (MCP-1/CCL2, MCP-2/CCL8, MCP-3/CCL7). In contrast to MCP-3/CCL7, parvoviral delivery of MCP-2/CCL8 into B78/H1 melanoma failed to inhibit tumor growth, partially due to proteolytic cleavage into inactive MCP-2/CCL8 missing five NH(2)-terminal residues. However, in an alternative tumor model, using HeLa cells, MCP-2/CCL8 retarded tumor development. These data indicate that optimal induction and delivery of MCP-2/CCL8 is counteracted by converting this chemokine into a receptor antagonist, thereby losing its anti-tumoral potential.