Chemokine isoforms and processing in inflammation and immunity

The chemokine receptor CCR8 is not a high-affinity receptor for the human chemokine CCL18

The primate-specific chemokine CCL18 is a potent chemoattractant for T cells and is expressed at elevated levels in several inflammatory diseases. However, the cognate receptor for CCL18 remains unconfirmed. Here, we describe attempts to validate a previous report that the chemokine receptor CCR8 is the human CCL18 receptor (Islam et al. J Exp Med. 2013, 210:1889-98). Two mouse pre-B cell lines (4DE4 and L1.2) exogenously expressing CCR8 exhibited robust migration in response to the known CCR8 ligand CCL1 but not to CCL18. Similarly, CCL1 but not CCL18 induced internalization of CCR8 on 4DE4 cells. CCR8 expressed on Chinese hamster ovarian (CHO) cells mediated robust G protein activation, inhibition of cAMP synthesis and β-arrestin2 recruitment in response to CCL1 but not CCL18. Several N- and C-terminal variants of CCL18 also failed to stimulate CCR8 activation. On the other hand, and as previously reported, CCL18 inhibited CCL11-stimulated migration of 4DE4 cells expressing the receptor CCR3. These data suggest that CCR8, at least in the absence of unidentified cofactors, does not function as a high affinity receptor for CCL18.

Naringenin: its chemistry and roles in neuroprotection

According to epidemiological research, as the population ages, neurological illnesses are becoming a bigger issue. Despite improvements in the treatment of these diseases, there are still widespread worries about how to find a long-lasting remedy. Several neurological diseases can be successfully treated with natural substances. As a result, current research has been concentrated on finding effective neuroprotective drugs with improved efficacy and fewer side effects. Naringenin is one potential treatment for neurodegenerative diseases. Many citrus fruits, tomatoes, bergamots, and other fruits are rich in naringenin, a flavonoid. This phytochemical is linked to a variety of biological functions. Naringenin has attracted a lot of interest for its ability to exhibit neuroprotection through several mechanisms. In the current article, we present evidence from the literature that naringenin reduces neurotoxicity and oxidative stress in brain tissues. Also, the literatures that are currently accessible shows that naringenin reduces neuroinflammation and other neurological anomalies. Additionally, we found several studies that touted naringenin as a promising anti-amyloidogenic, antidepressant, and neurotrophic treatment option. This review's major goal is to reflect on advancements in knowledge of the molecular processes that underlie naringenin's possible neuroprotective effects. Furthermore, this article also provides highlights of Naringenin with respect to its chemistry and pharmacokinetics.

Unveiling cytokine charge disparity as a potential mechanism for immune regulation

Cytokines are small signaling proteins that regulate the immune responses to infection and tissue damage. Surface charges of cytokines determine their in vivo fate in immune regulation, e.g., half-life and distribution. The overall negative charges in the extracellular microenvironment and the acidosis during inflammation and infection may differentially impact cytokines with different surface charges for fine-tuned immune regulation via controlling tissue residential properties. However, the trend and role of cytokine surface charges has yet to be elucidated in the literature. Interestingly, we have observed that most pro-inflammatory cytokines have a negative charge, while most anti-inflammatory cytokines and chemokines have a positive charge. In this review, we extensively examined the surface charges of all cytokines and chemokines, summarized the pharmacokinetics and tissue adhesion of major cytokines, and analyzed the link of surface charge with cytokine biodistribution, activation, and function in immune regulation. Additionally, we identified that the general trend of charge disparity between pro- and anti-inflammatory cytokines represents a unique opportunity to develop precise immune modulation approaches, which can be applied to many inflammation-associated diseases including solid tumors, chronic wounds, infection, and sepsis.

Plasma extracellular vesicle microRNAs reflecting the therapeutic effect of the CBP/β-catenin inhibitor PRI-724 in patients with liver cirrhosis

There is an unmet need for antifibrotic therapies to prevent the progression of liver cirrhosis. Previously, we conducted an exploratory trial to assess the safety and antifibrotic efficacy of PRI-724, a selective CBP/β-catenin inhibitor, in patients with liver cirrhosis. PRI-724 was well tolerated and exerted a potential antifibrotic effect. Here, we investigated whether the profiles of circulating microRNAs packaged in extracellular vesicles (EV-miRNAs) are associated with responses to liver fibrosis treatments. Eighteen patients who received PRI-724 for 12 weeks in a phase 1/2a study were classified as responders (n = 10) or non-responders (n = 8) based on changes in liver stiffness. Plasma samples were obtained before and after PRI-724 administration and the levels of EV-miRNAs were analyzed. Three miRNAs (miR-6510-5p, miR-6772-5p, and miR-4261) were identified as predictors of response or non-response to PRI-724, and the levels of three other miRNAs (miR-939-3p, miR-887-3p, and miR-7112-5p) correlated with the efficacy of treatment. Expression of miR-887-3p was detected in hepatocytes and was decreased significantly in liver tissue following PRI-724 treatment. In addition, transfection of a miR-887-3p mimic activated hepatic stellate cells. Thus, decreases in the miR-887-3p level in blood may reflect recovery from liver fibroses in patients with liver cirrhosis treated with PRI-724, although further validation studies are warranted to confirm this.

Natural carboxyterminal truncation of human CXCL10 attenuates glycosaminoglycan binding, CXCR3A signaling and lymphocyte chemotaxis, while retaining angiostatic activity

BACKGROUND

Interferon-γ-inducible protein of 10 kDa (IP-10/CXCL10) is a dual-function CXC chemokine that coordinates chemotaxis of activated T cells and natural killer (NK) cells via interaction with its G protein-coupled receptor (GPCR), CXC chemokine receptor 3 (CXCR3). As a consequence of natural posttranslational modifications, human CXCL10 exhibits a high degree of structural and functional heterogeneity. However, the biological effect of natural posttranslational processing of CXCL10 at the carboxy (C)-terminus has remained partially elusive. We studied CXCL10(1-73), lacking the four endmost C-terminal amino acids, which was previously identified in supernatant of cultured human fibroblasts and keratinocytes.

METHODS

Relative levels of CXCL10(1-73) and intact CXCL10(1-77) were determined in synovial fluids of patients with rheumatoid arthritis (RA) through tandem mass spectrometry. The production of CXCL10(1-73) was optimized through Fmoc-based solid phase peptide synthesis (SPPS) and a strategy to efficiently generate human CXCL10 proteoforms was introduced. CXCL10(1-73) was compared to intact CXCL10(1-77) using surface plasmon resonance for glycosaminoglycan (GAG) binding affinity, assays for cell migration, second messenger signaling downstream of CXCR3, and flow cytometry of CHO cells and primary human T lymphocytes and endothelial cells. Leukocyte recruitment in vivo upon intraperitoneal injection of CXCL10(1-73) was also evaluated.

RESULTS

Natural CXCL10(1-73) was more abundantly present compared to intact CXCL10(1-77) in synovial fluids of patients with RA. CXCL10(1-73) had diminished affinity for GAG including heparin, heparan sulfate and chondroitin sulfate A. Moreover, CXCL10(1-73) exhibited an attenuated capacity to induce CXCR3A-mediated signaling, as evidenced in calcium mobilization assays and through quantification of phosphorylated extracellular signal-regulated kinase-1/2 (ERK1/2) and protein kinase B/Akt. Furthermore, CXCL10(1-73) incited significantly less primary human T lymphocyte chemotaxis in vitro and peritoneal ingress of CXCR3+ T lymphocytes in mice. In contrast, loss of the four endmost C-terminal residues did not affect the inhibitory properties of CXCL10 on migration, proliferation, wound closure, phosphorylation of ERK1/2, and sprouting of human microvascular endothelial cells.

CONCLUSION

Our study shows that the C-terminal residues Lys74-Pro77 of CXCL10 are important for GAG binding, signaling through CXCR3A, T lymphocyte chemotaxis, but dispensable for angiostasis.

Chemokine N-terminal-derived peptides differentially regulate signaling by the receptors CCR1 and CCR5

Inflammatory chemokines are often elevated in disease settings, where the largest group of CC-chemokines are the macrophage inflammatory proteins (MIP), which are promiscuous for the receptors CCR1 and CCR5. MIP chemokines, such as CCL3 and CCL5 are processed at the N terminus, which influences signaling in a highly diverse manner. Here, we investigate the signaling capacity of peptides corresponding to truncated N termini. These 3-10-residue peptides displayed weak potency but, surprisingly, retained their signaling on CCR1. In contrast, none of the peptides generated a signal on CCR5, but a CCL3-derived tetrapeptide was a positive modulator boosting the signal of several chemokine variants on CCR5. In conclusion, chemokine N termini can be mimicked to produce small CCR1-selective agonists, as well as CCR5-selective modulators.

The double-edged role of neutrophil heterogeneity in inflammatory diseases and cancers

Neutrophils are important immune cells act as the body's first line of defense against infection and respond to diverse inflammatory cues. Many studies have demonstrated that neutrophils display plasticity in inflammatory diseases and cancers. Clarifying the role of neutrophil heterogeneity in inflammatory diseases and cancers will contribute to the development of novel treatment strategies. In this review, we have presented a review on the development of the understanding on neutrophil heterogeneity from the traditional perspective and a high-resolution viewpoint. A growing body of evidence has confirmed the double-edged role of neutrophils in inflammatory diseases and tumors. This may be due to a lack of precise understanding of the role of specific neutrophil subsets in the disease. Thus, elucidating specific neutrophil subsets involved in diseases would benefit the development of precision medicine. Thusly, we have summarized the relevance and actions of neutrophil heterogeneity in inflammatory diseases and cancers comprehensively. Meanwhile, we also discussed the potential intervention strategy for neutrophils. This review is intended to deepen our understanding of neutrophil heterogeneity in inflammatory diseases and cancers, while hold promise for precise treatment of neutrophil-related diseases.

The role of neutrophils in chorioamnionitis

Chorioamnionitis, commonly referred to as intrauterine infection or inflammation, is pathologically defined by neutrophil infiltration and inflammation at the maternal-fetal interface. Chorioamnionitis is the common complication during late pregnancy, which lead to a series of serious consequences, such as preterm labor, preterm premature rupture of the fetal membranes, and fetal inflammatory response syndrome. During infection, a large number of neutrophils migrate to the chorio-decidua in response to chemokines. Although neutrophils, a crucial part of innate immune cells, have strong anti-inflammatory properties, over-activating them can harm the body while also eliminating pathogens. This review concentrated on the latest studies on chorioamnionitis-related consequences as well as the function and malfunction of neutrophils. The release of neutrophil extracellular traps, production of reactive oxygen species, and degranulation from neutrophils during intrauterine infection, as well as their pathological roles in complications related to chorioamnionitis, were discussed in detail, offering fresh perspectives on the treatment of chorioamnionitis.

A review of the pleiotropic actions of the IFN-inducible CXC chemokine receptor 3 ligands in the synovial microenvironment

Chemokines are pivotal players in instigation and perpetuation of synovitis through leukocytes egress from the blood circulation into the inflamed articulation. Multitudinous literature addressing the involvement of the dual-function interferon (IFN)-inducible chemokines CXCL9, CXCL10 and CXCL11 in diseases characterized by chronic inflammatory arthritis emphasizes the need for detangling their etiopathological relevance. Through interaction with their mutual receptor CXC chemokine receptor 3 (CXCR3), the chemokines CXCL9, CXCL10 and CXCL11 exert their hallmark function of coordinating directional trafficking of CD4+ TH1 cells, CD8+ T cells, NK cells and NKT cells towards inflammatory niches. Among other (patho)physiological processes including infection, cancer, and angiostasis, IFN-inducible CXCR3 ligands have been implicated in autoinflammatory and autoimmune diseases. This review presents a comprehensive overview of the abundant presence of IFN-induced CXCR3 ligands in bodily fluids of patients with inflammatory arthritis, the outcomes of their selective depletion in rodent models, and the attempts at developing candidate drugs targeting the CXCR3 chemokine system. We further propose that the involvement of the CXCR3 binding chemokines in synovitis and joint remodeling encompasses more than solely the directional ingress of CXCR3-expressing leukocytes. The pleotropic actions of the IFN-inducible CXCR3 ligands in the synovial niche reiteratively illustrate the extensive complexity of the CXCR3 chemokine network, which is based on the intercommunion of IFN-inducible CXCR3 ligands with distinct CXCR3 isoforms, enzymes, cytokines, and infiltrated and resident cells present in the inflamed joints.

Mammalian Glycosylation Patterns Protect Citrullinated Chemokine MCP-1/CCL2 from Partial Degradation

Monocyte chemoattractant protein-1 (MCP-1/CCL2) is a potent chemotactic agent for monocytes, primarily produced by macrophages and endothelial cells. Significantly elevated levels of MCP-1/CCL2 were found in synovial fluids of patients with rheumatoid arthritis (RA), compared to osteoarthritis or other arthritis patients. Several studies suggested an important role for MCP-1 in the massive inflammation at the damaged joint, in part due to its chemotactic and angiogenic effects. It is a known fact that the post-translational modifications (PTMs) of proteins have a significant impact on their properties. In mammals, arginine residues within proteins can be converted into citrulline by peptidylarginine deiminase (PAD) enzymes. Anti-citrullinated protein antibodies (ACPA), recognizing these PTMs, have become a hallmark for rheumatoid arthritis (RA) and other autoimmune diseases and are important in diagnostics and prognosis. In previous studies, we found that citrullination converts the neutrophil attracting chemokine neutrophil-activating peptide 78 (ENA-78) into a potent macrophage chemoattractant. Here we report that both commercially available and recombinant bacterially produced MCP-1/CCL2 are rapidly (partially) degraded upon in vitro citrullination. However, properly glycosylated MCP-1/CCL2 produced by mammalian cells is protected against degradation during efficient citrullination. Site-directed mutagenesis of the potential glycosylation site at the asparagine-14 residue within human MCP-1 revealed lower expression levels in mammalian expression systems. The glycosylation-mediated recombinant chemokine stabilization allows the production of citrullinated MCP-1/CCL2, which can be effectively used to calibrate crucial assays, such as modified ELISAs.

Galectokines: The Promiscuous Relationship between Galectins and Cytokines

Galectins, a family of glycan-binding proteins, are well-known for their role in shaping the immune microenvironment. They can directly affect the activity and survival of different immune cell subtypes. Recent evidence suggests that galectins also indirectly affect the immune response by binding to members of another immunoregulatory protein family, i.e., cytokines. Such galectin-cytokine heterodimers, here referred to as galectokines, add a new layer of complexity to the regulation of immune homeostasis. Here, we summarize the current knowledge with regard to galectokine formation and function. We describe the known and potential mechanisms by which galectokines can help to shape the immune microenvironment. Finally, the outstanding questions and challenges for future research regarding the role of galectokines in immunomodulation are discussed.

Matrix Metalloproteinases: From Molecular Mechanisms to Physiology, Pathophysiology, and Pharmacology

The first matrix metalloproteinase (MMP) was discovered in 1962 from the tail of a tadpole by its ability to degrade collagen. As their name suggests, matrix metalloproteinases are proteases capable of remodeling the extracellular matrix. More recently, MMPs have been demonstrated to play numerous additional biologic roles in cell signaling, immune regulation, and transcriptional control, all of which are unrelated to the degradation of the extracellular matrix. In this review, we will present milestones and major discoveries of MMP research, including various clinical trials for the use of MMP inhibitors. We will discuss the reasons behind the failures of most MMP inhibitors for the treatment of cancer and inflammatory diseases. There are still misconceptions about the pathophysiological roles of MMPs and the best strategies to inhibit their detrimental functions. This review aims to discuss MMPs in preclinical models and human pathologies. We will discuss new biochemical tools to track their proteolytic activity in vivo and ex vivo, in addition to future pharmacological alternatives to inhibit their detrimental functions in diseases. SIGNIFICANCE STATEMENT: Matrix metalloproteinases (MMPs) have been implicated in most inflammatory, autoimmune, cancers, and pathogen-mediated diseases. Initially overlooked, MMP contributions can be both beneficial and detrimental in disease progression and resolution. Thousands of MMP substrates have been suggested, and a few hundred have been validated. After more than 60 years of MMP research, there remain intriguing enigmas to solve regarding their biological functions in diseases.

Identification of a conserved chemokine receptor motif that enables ligand discrimination

Extensive ligand-receptor promiscuity in the chemokine signaling system balances beneficial redundancy and specificity. However, this feature poses a major challenge to selectively modulate the system pharmacologically. Here, we identified a conserved cluster of three aromatic receptor residues that anchors the second extracellular loop (ECL2) to the top of receptor transmembrane helices (TM) 4 and 5 and enables recognition of both shared and specific characteristics of interacting chemokines. This cluster was essential for the activation of several chemokine receptors. Furthermore, characteristic motifs of the ß₁ strand and 30s loop make the two main CC-chemokine subgroups-the macrophage inflammatory proteins (MIPs) and monocyte chemoattractant proteins (MCPs)-differentially dependent on this cluster in the promiscuous receptors CCR1, CCR2, and CCR5. The cluster additionally enabled CCR1 and CCR5 to discriminate between closely related MIPs based on the N terminus of the chemokine. G protein signaling and β-arrestin2 recruitment assays confirmed the importance of the conserved cluster in receptor discrimination of chemokine ligands. This extracellular site may facilitate the development of chemokine-related therapeutics.

Multi-omic landscaping of human midbrains identifies disease-relevant molecular targets and pathways in advanced-stage Parkinson's disease

BACKGROUND

Parkinson's disease (PD) is the second most common neurodegenerative disorder whose prevalence is rapidly increasing worldwide. The molecular mechanisms underpinning the pathophysiology of sporadic PD remain incompletely understood. Therefore, causative therapies are still elusive. To obtain a more integrative view of disease-mediated alterations, we investigated the molecular landscape of PD in human post-mortem midbrains, a region that is highly affected during the disease process.

METHODS

Tissue from 19 PD patients and 12 controls were obtained from the Parkinson's UK Brain Bank and subjected to multi-omic analyses: small and total RNA sequencing was performed on an Illumina's HiSeq4000, while proteomics experiments were performed in a hybrid triple quadrupole-time of flight mass spectrometer (TripleTOF5600+) following quantitative sequential window acquisition of all theoretical mass spectra. Differential expression analyses were performed with customized frameworks based on DESeq2 (for RNA sequencing) and with Perseus v.1.5.6.0 (for proteomics). Custom pipelines in R were used for integrative studies.

RESULTS

Our analyses revealed multiple deregulated molecular targets linked to known disease mechanisms in PD as well as to novel processes. We have identified and experimentally validated (quantitative real-time polymerase chain reaction/western blotting) several PD-deregulated molecular candidates, including miR-539-3p, miR-376a-5p, miR-218-5p and miR-369-3p, the valid miRNA-mRNA interacting pairs miR-218-5p/RAB6C and miR-369-3p/GTF2H3, as well as multiple proteins, such as CHI3L1, HSPA1B, FNIP2 and TH. Vertical integration of multi-omic analyses allowed validating disease-mediated alterations across different molecular layers. Next to the identification of individual molecular targets in all explored omics layers, functional annotation of differentially expressed molecules showed an enrichment of pathways related to neuroinflammation, mitochondrial dysfunction and defects in synaptic function.

CONCLUSIONS

This comprehensive assessment of PD-affected and control human midbrains revealed multiple molecular targets and networks that are relevant to the disease mechanism of advanced PD. The integrative analyses of multiple omics layers underscore the importance of neuroinflammation, immune response activation, mitochondrial and synaptic dysfunction as putative therapeutic targets for advanced PD.

The Chemokine Systems at the Crossroads of Inflammation and Energy Metabolism in the Development of Obesity

Obesity is characterized as a complex and multifactorial excess accretion of adipose tissue accompanied with alterations in the immune and metabolic responses. Although the chemokine systems have been documented to be involved in the control of tissue inflammation and metabolism, the dual role of chemokines and chemokine receptors in the pathogenesis of the inflammatory milieu and dysregulated energy metabolism in obesity remains elusive. The objective of this review is to present an update on the link between chemokines and obesity-related inflammation and metabolism dysregulation under the light of recent knowledge, which may present important therapeutic targets that could control obesity-associated immune and metabolic disorders and chronic complications in the near future. In addition, the cellular and molecular mechanisms of chemokines and chemokine receptors including the potential effect of post-translational modification of chemokines in the regulation of inflammation and energy metabolism will be discussed in this review.

Circulating CXCL13 could be served as a biomarker for chronic lymphocytic leukemia severity

BACKGROUND

Recent reports indicated the importance of chemotractants CXCL-13 in solid tumors and lymphoid malignancies. However, the prognostic value of the mentioned cytokines as biomarkers in chronic lymphocytic leukemia patient's remains to be identified. Therefore; this study was designed in order to address the relation between CXCL-13 concentrations levels and markers of severity in CLL patients.

METHODS

Our study included 150 CLL patients and 20 controls. Serum CXCL-13 was determined by ELISA for CLL patients at diagnosis as well as controls.

RESULTS

The serum CXCL-13 levels were significantly higher in CLL patients as compared to controls. The high CXCL-13 concentration levels was significantly associated with high number of smudge cells; high LDH; high grade of Rai stage, short time to first treatment (TTT). Cox regression analysis was conducted for prediction of TTT, using age, gender, WBCs, smudge cells, CXCL-13, LDH, ZAP70, CD38, β2-microglobulin, Rai staging as covariates. High LDH, CXCL-13 and CD38% were significantly independent predictor for shorter TTT.

CONCLUSION

High CXCL-13 serum levels at CLL diagnosis is correlated with other markers of disease activity; and could be served as biomarkers that predict CLL patient's outcome.

The Role of Post-Translational Modifications of Chemokines by CD26 in Cancer

Chemokines are a large family of small chemotactic cytokines that fulfill a central function in cancer. Both tumor-promoting and -impeding roles have been ascribed to chemokines, which they exert in a direct or indirect manner. An important post-translational modification that regulates chemokine activity is the NH₂-terminal truncation by peptidases. CD26 is a dipeptidyl peptidase (DPPIV), which typically clips a NH₂-terminal dipeptide from the chemokine. With a certain degree of selectivity in terms of chemokine substrate, CD26 only recognizes chemokines with a penultimate proline or alanine. Chemokines can be protected against CD26 recognition by specific amino acid residues within the chemokine structure, by oligomerization or by binding to cellular glycosaminoglycans (GAGs). Upon truncation, the binding affinity for receptors and GAGs is altered, which influences chemokine function. The consequences of CD26-mediated clipping vary, as unchanged, enhanced, and reduced activities are reported. In tumors, CD26 most likely has the most profound effect on CXCL12 and the interferon (IFN)-inducible CXCR3 ligands, which are converted into receptor antagonists upon truncation. Depending on the tumor type, expression of CD26 is upregulated or downregulated and often results in the preferential generation of the chemokine isoform most favorable for tumor progression. Considering the tight relationship between chemokine sequence and chemokine binding specificity, molecules with the appropriate characteristics can be chemically engineered to provide innovative therapeutic strategies in a cancer setting.

Inflammation and tumor progression: signaling pathways and targeted intervention

Cancer development and its response to therapy are regulated by inflammation, which either promotes or suppresses tumor progression, potentially displaying opposing effects on therapeutic outcomes. Chronic inflammation facilitates tumor progression and treatment resistance, whereas induction of acute inflammatory reactions often stimulates the maturation of dendritic cells (DCs) and antigen presentation, leading to anti-tumor immune responses. In addition, multiple signaling pathways, such as nuclear factor kappa B (NF-kB), Janus kinase/signal transducers and activators of transcription (JAK-STAT), toll-like receptor (TLR) pathways, cGAS/STING, and mitogen-activated protein kinase (MAPK); inflammatory factors, including cytokines (e.g., interleukin (IL), interferon (IFN), and tumor necrosis factor (TNF)-α), chemokines (e.g., C-C motif chemokine ligands (CCLs) and C-X-C motif chemokine ligands (CXCLs)), growth factors (e.g., vascular endothelial growth factor (VEGF), transforming growth factor (TGF)-β), and inflammasome; as well as inflammatory metabolites including prostaglandins, leukotrienes, thromboxane, and specialized proresolving mediators (SPM), have been identified as pivotal regulators of the initiation and resolution of inflammation. Nowadays, local irradiation, recombinant cytokines, neutralizing antibodies, small-molecule inhibitors, DC vaccines, oncolytic viruses, TLR agonists, and SPM have been developed to specifically modulate inflammation in cancer therapy, with some of these factors already undergoing clinical trials. Herein, we discuss the initiation and resolution of inflammation, the crosstalk between tumor development and inflammatory processes. We also highlight potential targets for harnessing inflammation in the treatment of cancer.

Association of the CXCL9-CXCR3 and CXCL13-CXCR5 axes with B-cell trafficking in giant cell arteritis and polymyalgia rheumatica

OBJECTIVE

B-cells are present in the inflamed arteries of giant cell arteritis (GCA) patients and a disturbed B-cell homeostasis is reported in peripheral blood of both GCA and the overlapping disease polymyalgia rheumatica (PMR). In this study, we aimed to investigate chemokine-chemokine receptor axes governing the migration of B-cells in GCA and PMR.

METHODS

We performed Luminex screening assay for serum levels of B-cell related chemokines in treatment-naïve GCA (n = 41), PMR (n = 31) and age- and sex matched healthy controls (HC, n = 34). Expression of chemokine receptors on circulating B-cell subsets were investigated by flow cytometry. Immunohistochemistry was performed on GCA temporal artery (n = 14) and aorta (n = 10) and on atherosclerosis aorta (n = 10) tissue.

RESULTS

The chemokines CXCL9 and CXCL13 were significantly increased in the circulation of treatment-naïve GCA and PMR patients. CXCL13 increased even further after three months of glucocorticoid treatment. At baseline CXCL13 correlated with disease activity markers. Peripheral CXCR3+ and CXCR5+ switched memory B-cells were significantly reduced in both patient groups and correlated inversely with their complementary chemokines CXCL9 and CXCL13. At the arterial lesions in GCA, CXCR3+ and CXCR5+ B-cells were observed in areas with high CXCL9 and CXCL13 expression.

CONCLUSION

Changes in systemic and local chemokine and chemokine receptor pathways related to B-cell migration were observed in GCA and PMR mainly in the CXCL9-CXCR3 and CXCL13-CXCR5 axes. These changes can contribute to homing and organization of B-cells in the vessel wall and provide further evidence for an active involvement of B-cells in GCA and PMR.

Active Ratio Test (ART) as a Novel Diagnostic for Ovarian Cancer

Background: Despite substantial effort, there remains a lack of biomarker-based, clinically relevant testing for the accurate, non-invasive diagnostic or prognostic profiling of epithelial ovarian cancers (EOC). Our previous work demonstrated that whilst the inflammatory marker C-X-C motif chemokine ligand 10 (CXCL10) has prognostic relevance in ovarian cancer, its use is complicated by the presence of multiple, N-terminally modified variants, mediated by several enzymes including Dipeptidyl Peptidase 4 (DPP4). Methods: In this study, we provide the first evidence for the “Active Ratio Test” (ART) as a novel method to measure biologically relevant CXCL10 proteoforms in clinical samples. Results: In a cohort of 275 patients, ART accurately differentiated patients with malignant EOCs from those with benign gynaecological conditions (AUC 0.8617) and significantly out-performed CA125 alone. Moreover, ART combined with the measurement of CA125 and DPP4 significantly increased prognostic performance (AUC 0.9511; sensitivity 90.0%; specificity 91.7%; Cohen’s d > 1) for EOC detection. Conclusion: Our data demonstrate that ART provides a useful method to accurately discriminate between patients with benign versus malignant EOC, and highlights their relevance to ovarian cancer diagnosis. This marker combination may also be applicable in broader screening applications, to identify or discriminate benign from malignant disease in asymptomatic women.

From ELISA to Immunosorbent Tandem Mass Spectrometry Proteoform Analysis: The Example of CXCL8/Interleukin-8

With ELISAs one detects the ensemble of immunoreactive molecules in biological samples. For biomolecules undergoing proteolysis for activation, potentiation or inhibition, other techniques are necessary to study biology. Here we develop methodology that combines immunosorbent sample preparation and nano-scale liquid chromatography—tandem mass spectrometry (nano-LC-MS/MS) for proteoform analysis (ISTAMPA) and apply this to the aglycosyl chemokine CXCL8. CXCL8, the most powerful human chemokine with neutrophil chemotactic and –activating properties, occurs in different NH₂-terminal proteoforms due to its susceptibility to site-specific proteolytic modification. Specific proteoforms display up to 30-fold enhanced activity. The immunosorbent ion trap top-down mass spectrometry-based approach for proteoform analysis allows for simultaneous detection and quantification of full-length CXCL8(1-77), elongated CXCL8(-2-77) and all naturally occurring truncated CXCL8 forms in biological samples. For the first time we demonstrate site-specific proteolytic activation of CXCL8 in synovial fluids from patients with chronic joint inflammation and address the importance of sample collection and processing.

Roles of neutrophil granule proteins in orchestrating inflammation and immunity

Neutrophil granulocytes form the first line of host defense against invading pathogens and tissue injury. They are rapidly recruited from the blood to the affected sites, where they deploy an impressive arsenal of effectors to eliminate invading microbes and damaged cells. This capacity is endowed in part by readily mobilizable proteins acquired during granulopoiesis and stored in multiple types of cytosolic granules with each granule type containing a unique cargo. Once released, granule proteins contribute to killing bacteria within the phagosome or the extracellular milieu, but are also capable of inflicting collateral tissue damage. Neutrophil-driven inflammation underlies many common diseases. Research over the last decade has documented neutrophil heterogeneity and functional versatility far beyond their antimicrobial function. Emerging evidence indicates that neutrophils utilize granule proteins to interact with innate and adaptive immune cells and orchestrate the inflammatory response. Granule proteins have been identified as important modulators of neutrophil trafficking, reverse transendothelial migration, phagocytosis, neutrophil life span, neutrophil extracellular trap formation, efferocytosis, cytokine activity, and autoimmunity. Hence, defining their roles within the inflammatory locus is critical for minimizing damage to the neighboring tissue and return to homeostasis. Here, we provide an overview of recent advances in the regulation of degranulation, granule protein functions, and signaling in modulating neutrophil-mediated immunity. We also discuss how targeting granule proteins and/or signaling could be harnessed for therapeutic benefits.

Natural Marine and Terrestrial Compounds as Modulators of Matrix Metalloproteinases-2 (MMP-2) and MMP-9 in Alzheimer's Disease

Several studies have reported neuroprotective effects by natural products. A wide range of natural compounds have been investigated, and some of these may play a beneficial role in Alzheimer's disease (AD) progression. Matrix metalloproteinases (MMPs), a family of zinc-dependent endopeptidases, have been implicated in AD. In particular, MMP-2 and MMP-9 are able to trigger several neuroinflammatory and neurodegenerative pathways. In this review, we summarize and discuss existing literature on natural marine and terrestrial compounds, as well as their ability to modulate MMP-2 and MMP-9, and we evaluate their potential as therapeutic compounds for neurodegenerative and neuroinflammatory diseases, with a focus on Alzheimer's disease.

Examination of Oral Squamous Cell Carcinoma and Precancerous Lesions Using Proximity Extension Assay and Salivary RNA Quantification

Saliva is an easy-to access body fluid with high diagnostic potential. The utilization of saliva for oral cancer diagnosis can be an attractive possibility. Besides the oral cancer, it is important to better understand the precancerous lesions such as oral lichen planus (OLP) and leukoplakia (OLK). In order to examine the changes of salivary proteins in controls, patients with oral cancer, and patients with precancerous conditions, proximity extension assay was utilized. Some proteins and functions were characteristic to the examined groups and can serve as a starting point for further biomarker studies. The different nature of OLK and OLP was demonstrated, showing the malignant transformation and the inflammation as the prominent biological processes in the OLK and OLP, respectively. The salivary level of IL6 was verified using quantitative ELISA and the mRNA level was also studied. Elevated IL6 levels could be detected in precancerous groups compared to controls.

Naringenin attenuates experimental autoimmune encephalomyelitis by protecting the intact of blood-brain barrier and controlling inflammatory cell migration

Targeting pathogenic immune cell trafficking poses an attractive opportunity to attenuate autoimmune disorders such as multiple sclerosis (MS). MS and its animal model, experimental autoimmune encephalomyelitis (EAE), are characterized by the immune cells-mediated demyelination and neurodegeneration of the central nervous system (CNS). Our previous study has proven that dietary naringenin ameliorates EAE clinical symptoms via reducing the CNS cell infiltration. The present study examined the beneficial effects of naringenin on maintaining the blood-brain barrier in EAE mice via dietary naringenin intervention. The results showed that naringenin-treated EAE mice had an intact blood-CNS barrier by increasing tight junction-associated factors and decreasing Evans Blue dye in the CNS. Naringenin decreased the accumulation and maturation of conventional dendritic cells (cDCs), CCL19, and CCR7 in the CNS. Also, naringenin blocked the chemotaxis and antigen-presenting function of cDCs that resulted in reducing T-cell secreting cytokines (IFN-γ, IL-17, and IL-6) in the spleen. Importantly, naringenin blocked pathogenic T cells infiltrated into the CNS and attenuates passive EAE. Therefore, by blocking chemokine-mediated migration of DCs and pathogenic T cells into the CNS, naringenin attenuates EAE pathogenesis and might be a potential candidate for the treatment of autoimmune diseases, such as MS and other chronic T-cell mediated autoimmune diseases.

Citrullination as a novel posttranslational modification of matrix metalloproteinases

Matrix metalloproteinases (MMPs) are enzymes with critical roles in biology and pathology. Glycosylation, nitrosylation and proteolysis are known posttranslational modifications (PTMs) regulating intrinsically the activities of MMPs. We discovered MMP citrullination by peptidyl arginine deiminases (PADs) as a new PTM. Upon hypercitrullination, MMP-9 acquired a higher affinity for gelatin than control MMP-9. Furthermore, hypercitrullinated proMMP-9 was more efficiently activated by MMP-3 compared to control MMP-9. JNJ0966, a specific therapeutic inhibitor of MMP-9 activation, inhibited the activation of hypercitrullinated proMMP-9 by MMP-3 significantly less in comparison with control proMMP-9. The presence of citrullinated/homocitrullinated MMP-9 was detected in vivo in neutrophil-rich sputum samples of cystic fibrosis patients. In addition to citrullination of MMP-9, we report efficient citrullination of MMP-1 and lower citrullination levels of MMP-3 and MMP-13 by PAD2 in vitro. In conclusion, citrullination of MMPs is a new PTM worthy of additional biochemical and biological studies.

Integration of RNA-seq and RNAi provides a novel insight into the immune responses of Epinephelus coioides to the impB gene of Pseudomonas plecoglossicida

Pseudomonas plecoglossicida is a Gram-negative bacterium that causes visceral white spot disease in Epinephelus coioides and leads to severe aquatic economic losses. The RNA-seq results of a previous study showed that the expression of the impB gene in P. plecoglossicida was significantly upregulated during infection. Four shRNAs were designed and synthesized to silence the impB gene in P. plecoglossicida, and the maximum silencing efficiency was 95.2%. Intraperitoneal injection of the impB-RNAi strain of P. plecoglossicida did not cause E. coioides death, and the spleens of infected fish did not show significant clinical symptoms. Although the injection of the mutant strain increased the antibody titer in E. coioides serum, it could not effectively protect E. coioides against wild strain infection. Compared with E. coioides infected with the wild type strain, the RNA-seq results for E. coioides infected with the impB-RNAi strain differed greatly. The KEGG enrichment analysis showed that key genes of the chemokine signalling pathway of E. coioides were downregulated by the silencing of impB in P. plecoglossicida. Infection with the impB-RNAi strain of P. plecoglossicida through injection did not produce good immune protection against E. coioides. The present study provides a novel insight into the immune responses of E. coioides to the impB gene of P. plecoglossicida.

Chronic endometritis and reproductive failure: Role of syndecan-1

Chronic endometritis (CE) is an unusual inflammatory condition characterized by endometrial plasmacyte infiltration. It has a high prevalence in women with reproductive failure. Because of its characteristic localization patterns and molecular functions, syndecan-1 has been identified as a biomarker of plasmacyte, and syndecan-1 immunohistochemistry (IHC) becomes the most dependable diagnostic method for CE. In this review, we discuss the association between CE and reproductive failure, the clinicopathological characterization of CE, the function and expression of syndecan-1, the progress of syndecan-1 IHC in the diagnosis of CE, and the prediction of reproductive outcome.

Chemokines in allergic conjunctivitis

PURPOSE OF REVIEW

Chemokines are a large group of low molecular weight cytokines that attract and activate leukocytes throughout the body and therefore have a key role in the framework of late-phase allergic responses. The purpose of this article is to provide an overview of the main chemokines involved in allergic conjunctivitis, their primary functions and their physiological roles, and therapies targeted at chemokines and their receptors for ocular allergic diseases.

RECENT FINDINGS

In recent years, there have been considerable advances in the understanding of ocular pathophysiology of ocular surface inflammatory diseases including both allergic eye diseases and dry eye syndrome. Several therapies being developed for dry eye inflammation are recognized as possible therapies for ocular allergic diseases as there are often common chemokines involved in both disease spectra.

SUMMARY

Chemokines represent an integral part of the late-phase cascade of ocular allergic inflammation. A deep understanding of specific chemokines and their interactions will help in targeting therapies to effectively manage ocular clinical findings and symptoms of allergic eye disease.

Bivalent Inhibitor with Selectivity for Trimeric MMP-9 Amplifies Neutrophil Chemotaxis and Enables Functional Studies on MMP-9 Proteoforms

A fundamental part of the immune response to infection or injury is leukocyte migration. Matrix metalloproteinases (MMPs) are a class of secreted or cell-bound endopeptidases, implicated in every step of the process of inflammatory cell migration. Hence, specific inhibition of MMPs is an interesting approach to control inflammation. We evaluated the potential of a bivalent carboxylate inhibitor to selectively inhibit the trimeric proteoform of MMP-9 and compared this with a corresponding monovalent inhibitor. The bivalent inhibitor efficiently inhibited trimeric MMP-9 (IC₅₀ = 0.1 nM), with at least 500-fold selectivity for MMP-9 trimers over monomers. Surprisingly, in a mouse model for chemotaxis, the bivalent inhibitor amplified leukocyte influxes towards lipopolysaccharide-induced inflammation. We verified by microscopic and flow cytometry analysis increased amounts of neutrophils. In a mouse model for endotoxin shock, mice treated with the bivalent inhibitor had significantly increased levels of MMP-9 in plasma and lungs, indicative for increased inflammation. In conclusion, we propose a new role for MMP-9 trimers in tempering excessive neutrophil migration. In addition, we have identified a small molecule inhibitor with a high selectivity for the trimeric proteoform of MMP-9, which will allow further research on the functions of MMP-9 proteoforms.

Neutrophils: Underestimated Players in the Pathogenesis of Multiple Sclerosis (MS)

Neutrophils are the most abundant circulating and first-responding innate myeloid cells and have so far been underestimated in the context of multiple sclerosis (MS). MS is the most frequent, immune-mediated, inflammatory disease of the central nervous system. MS is treatable but not curable and its cause(s) and pathogenesis remain elusive. The involvement of neutrophils in MS pathogenesis has been suggested by the use of preclinical animal disease models, as well as on the basis of patient sample analysis. In this review, we provide an overview of the possible mechanisms and functions by which neutrophils may contribute to the development and pathology of MS. Neutrophils display a broad variety of effector functions enabling disease pathogenesis, including (1) the release of inflammatory mediators and enzymes, such as interleukin-1β, myeloperoxidase and various proteinases, (2) destruction and phagocytosis of myelin (as debris), (3) release of neutrophil extracellular traps, (4) production of reactive oxygen species, (5) breakdown of the blood-brain barrier and (6) generation and presentation of autoantigens. An important question relates to the issue of whether neutrophils exhibit a predominantly proinflammatory function or are also implicated in the resolution of chronic inflammatory responses in MS.

Protease propeptide structures, mechanisms of activation, and functions

Proteases are a diverse group of hydrolytic enzymes, ranging from single-domain catalytic molecules to sophisticated multi-functional macromolecules. Human proteases are divided into five mechanistic classes: aspartate, cysteine, metallo, serine and threonine proteases, based on the catalytic mechanism of hydrolysis. As a protective mechanism against uncontrolled proteolysis, proteases are often produced and secreted as inactive precursors, called zymogens, containing inhibitory N-terminal propeptides. Protease propeptide structures vary considerably in length, ranging from dipeptides and propeptides of about 10 amino acids to complex multifunctional prodomains with hundreds of residues. Interestingly, sequence analysis of the different protease domains has demonstrated that propeptide sequences present higher heterogeneity compared with their catalytic domains. Therefore, we suggest that protease inhibition targeting propeptides might be more specific and have less off-target effects than classical inhibitors. The roles of propeptides, besides keeping protease latency, include correct folding of proteases, compartmentalization, liganding, and functional modulation. Changes in the propeptide sequence, thus, have a tremendous impact on the cognate enzymes. Small modifications of the propeptide sequences modulate the activity of the enzymes, which may be useful as a therapeutic strategy. This review provides an overview of known human proteases, with a focus on the role of their propeptides. We review propeptide functions, activation mechanisms, and possible therapeutic applications.

Cholinergic agonists inhibit proliferation of human fibroblast-like synoviocytes and monocytic cell lines and reduce VEGF and MMPs expression by these cells

Background and purpose: Rheumatoid arthritis (RA) is a chronic autoimmune disease characterized by inflammation and joint destruction. Excessive proliferation of fibroblast-like synoviocytes (FLS) and over-expression of angiogenic factors play a crucial role in pannus formation and joint destruction in RA. Clarification of the role of cholinergic agonists in modulation of inflammation and immune system reactions is progressively ongoing. In this study, the anti-angiogenic effect of two cholinergic agonists, nicotine and ARR17779, on human FLS, and monocytic cell lines (U937) was evaluated.Experimental approach: The cells were cultured in DMEM supplemented with 10% FBS and treated with different doses of nicotine and ARR17779 in the presence of TNF-α, LPS, and IFN-γ. After 48 h, cell number was counted in different groups. After RNA extraction, cDNA was synthesized and the expression of VEGF and MMPs has been evaluated by real-time PCR using specific primers and probes. VEGF was assayed in U937 cell line supernatant using ELISA method.Key results: Both nicotine and ARR17779 inhibited FLS and U937 cell proliferation. Cholinergic agonists reduced the expression of MMPs and VEGF. VEGF level in supernatant of U937 cells treated with cholinergic agonists was also reduced.Conclusion and implications: Our results suggest that cholinergic agonists can modulate pathological conditions related to pannus formation in in-vitro conditions. Based on these results, cholinergic agonists can be considered as novel therapeutic options in RA. Further animal studies are needed before introducing these agents into clinical uses.

Baked Bread Enhances the Immune Response and the Catabolism in the Human Body in Comparison with Steamed Bread

It is unclear whether different processing methods change the biological functions of foods and how these functions are evaluated in the human body. Here, steamed bread and baked bread, the traditional staple foods in China and many Western countries, were made by steaming and baking, respectively, using one piece of fermented wheat dough and then consumed by 16 healthy young volunteers. By detecting 38 cytokines, 12 metabolic enzymes, glucose, lactate, and nicotinamide adenine dinucleotide (NADH) in the serum, the cytokine network and central metabolic pathway network were investigated to compare the effects of the two staple foods on immunity and metabolism. Compared with steamed bread, baked bread increased (p < 0.05) concentrations of fractalkine and macrophage-derived chemokine, decreased (p < 0.05) the concentration of interleukin-1RA, increased (p < 0.05) the expression level of phosphofructokinase, and decreased (p < 0.05) the expression level of glucose-6-phosphate dehydrogenase in the serum. Two network analyses indicated that baked bread, as compared to the steamed bread, enhanced communication between immune cells, increased catabolism, and decreased anabolism. Further, a correlation analysis of cytokines and metabolic enzymes suggested that the two staple foods may affect metabolism by regulating the secretion of cytokines. These findings highlight how the same raw food material processed by different methods may have different impacts on immunity and metabolism in humans.

On the Neuroprotective Effects of Naringenin: Pharmacological Targets, Signaling Pathways, Molecular Mechanisms, and Clinical Perspective

As a group of progressive, chronic, and disabling disorders, neurodegenerative diseases (NDs) affect millions of people worldwide, and are on the rise. NDs are known as the gradual loss of neurons; however, their pathophysiological mechanisms have not been precisely revealed. Due to the complex pathophysiological mechanisms behind the neurodegeneration, investigating effective and multi-target treatments has remained a clinical challenge. Besides, appropriate neuroprotective agents are still lacking, which raises the need for new therapeutic agents. In recent years, several reports have introduced naturally-derived compounds as promising alternative treatments for NDs. Among natural entities, flavonoids are multi-target alternatives affecting different pathogenesis mechanisms in neurodegeneration. Naringenin is a natural flavonoid possessing neuroprotective activities. Increasing evidence has attained special attention on the variety of therapeutic targets along with complex signaling pathways for naringenin, which suggest its possible therapeutic applications in several NDs. Here, in this review, the neuroprotective effects of naringenin, as well as its related pharmacological targets, signaling pathways, molecular mechanisms, and clinical perspective, are described. Moreover, the need to develop novel naringenin delivery systems is also discussed to solve its widespread pharmacokinetic limitation.

Elevated Serum Levels of Monocyte Chemotactic Protein-1/Chemokine C-C Motif Ligand 2 are Linked to Disease Severity in Patients with Fibromyalgia Syndrome

Background:

Elevated levels of monocyte chemotactic protein-1/chemokine C-C motif ligand 2 have been identified in fibromyalgia patients.

Aims:

To examine the potential association among serum levels of monocyte chemotactic protein-1/chemokine C-C motif ligand 2 with disease severity of fibromyalgia.

Study Design:

Cross-sectional study.

Methods:

Seventy-nine female patients with fibromyalgia and 75 healthy normal controls were included in our study. Serum levels of monocyte chemotactic protein-1/chemokine C-C motif ligand 2 were detected by enzyme-linked immune sorbent assays. The existence of tender points was evaluated based on the standardized manual tender point examination. Pressure pain thresholds at the knees, and bilateral trapezius muscles were measured with an algometer. A visual analog scale and the Revised Fibromyalgia Impact Questionnaire were utilized to assess the degree of pain and functional abilities.

Results:

Serum levels of monocyte chemotactic protein-1/chemokine C-C motif ligand 2 were significantly greater in patients with fibromyalgia compared with healthy controls (151.6±31.9 pg/mL vs 103.3±25.2 pg/mL, p<0.001). Patients with severe fibromyalgia had significantly higher serum levels of chemokine C-C motif ligand 2 than patients with mild and moderate fibromyalgia (173.1±21.9 pg/mL vs 151.0.0±35.1 pg/mL, p=0.01). Patients with moderate fibromyalgia revealed markedly augmented serum levels of chemokine C-C motif ligand 2 compared with patients with mild fibromyalgia (151.0±35.1 pg/mL vs 133.3±23.9 pg/mL, p=0.03). Serum levels of chemokine C-C motif ligand 2 were positively associated with tender point scores (r=0.455, p<0.001). In addition, serum levels of chemokine C-C motif ligand 2 were positively associated with pressure pain thresholds in both knees and bilateral trapezius muscles (knees: r=-0.349, p=0.002; trapezius muscles: r=-0.318, p=0.004). Finally, we found elevated serum levels of chemokine C-C motif ligand were also positively associated with the visual analog scale (r=0.368, p=0.001), and the Fibromyalgia Impact Questionnaire score (r=0.401, p<0.001).

Conclusion:

Elevated serum levels of monocyte chemotactic protein-1/chemokine C-C motif ligand 2 are linked to disease severity of fibromyalgia. Therapeutic interventions inhibiting monocyte chemotactic protein-1/chemokine C-C motif ligand 2 in fibromyalgia deserve additional studies.

Citrullinated Peptide Epitope Targets Therapeutic Nanoparticles to Human Neutrophils

Multiple drugs have been proposed for reducing harsh symptoms of human rheumatic diseases. However, a targeted therapy with mild to no side effects is still missing. In this study, we have prepared and tested a series of therapeutic nanoparticles for specific targeting of human neutrophils associated with rheumatoid arthritis. In doing this, a series of citrullinated peptide epitopes derived from human proteins, fibrinogen, vimentin, and histone 3, were screened with regard to specific recognition of neutrophils. The most potent epitope proved to be a mutated fragment of an alpha chain in human fibrinogen. Next, a straightforward synthetic strategy was developed for nanoparticles decorated with this citrullinated peptide epitope and an antisense oligonucleotide targeting disease associated microRNA miR-125b-5p. Our study shows that the nanoparticles specifically recognize neutrophils and knock down miR-125b-5p, with no apparent toxicity to human cells. In contrast to organic dendrimers, chitosan-hyaluronic acid formulations do not activate human innate immune response. Our data proves that the strategy we report herein is effective in developing peptide epitopes for decorating delivery vehicles bearing biological drugs, targeted to a specific cell type.

Biased Signaling of CCL21 and CCL19 Does Not Rely on N-Terminal Differences, but Markedly on the Chemokine Core Domains and Extracellular Loop 2 of CCR7

Chemokine receptors play important roles in the immune system and are linked to several human diseases. Targeting chemokine receptors have so far shown very little success owing to, to some extent, the promiscuity of the immune system and the high degree of biased signaling within it. CCR7 and its two endogenous ligands display biased signaling and here we investigate the differences between the two ligands, CCL21 and CCL19, with respect to their biased activation of CCR7. We use bystander bioluminescence resonance energy transfer (BRET) based signaling assays and Transwell migration assays to determine (A) how swapping of domains between the two ligands affect their signaling patterns and (B) how receptor mutagenesis impacts signaling. Using chimeric ligands we find that the chemokine core domains are central for determining signaling outcome as the lack of β-arrestin-2 recruitment displayed by CCL21 is linked to its core domain and not N-terminus. Through a mutagenesis screen, we identify the extracellular domains of CCR7 to be important for both ligands and show that the two chemokines interact differentially with extracellular loop 2 (ECL-2). By using in silico modeling, we propose a link between ECL-2 interaction and CCR7 signal transduction. Our mutagenesis study also suggests a lysine in the top of TM3, K130^3.26, to be important for G protein signaling, but not β-arrestin-2 recruitment. Taken together, the bias in CCR7 between CCL19 and CCL21 relies on the chemokine core domains, where interactions with ECL-2 seem particularly important. Moreover, TM3 selectively regulates G protein signaling as found for other chemokine receptors.

Metalloproteinases mediate diabetes-induced retinal neuropathy and vasculopathy

Matrix metalloproteinases (MMPs) and related metalloproteinases with a disintegrin domain (ADAMs) have become interesting probes and targets in eye diseases, including diabetic retinopathy. We here summarize recent data about MMPs and ADAMs in retinopathies. Retinal diseases range from rare genetic afflictions to diabetic retinopathy, the latter of which is reaching epidemic proportions. MMPs and ADAMs play roles in normal eye development and in disease states, not only in local proteolysis but also signaling functions mediated by specific protein domains, interacting with cell surface receptors. In proliferative diabetic retinopathy, inflammation, hypoxia-induced vascular endothelial growth factor and oxidative stress collectively stimulate the production, activation and signaling functions of pro-MMP-9. This leads to angiogenesis, destruction of neuroprotective prominin-1, loss of photoreceptors and blood-retina barrier breakdown. Biological inhibition of proteolysis and control of signaling functions are executed by the tissue inhibitors of metalloproteases (TIMPs). Angiogenic, inflammatory and fibrotic reactions, in which MMPs, ADAMs and TIMPs are involved, co-determine common eye diseases. Therefore, visions about the use of these proteases as biomarkers and as targets for therapeutic inhibitors, including small molecule inhibitors and monoclonal antibodies, may lead to breakthroughs in tissue regeneration, maintenance of photoreceptors and neuroprotection.

CXCL13 and Its Receptor CXCR5 in Cancer: Inflammation, Immune Response, and Beyond

It is well-established that the chemokine C-X-C motif ligand 13 (CXCL13) and its receptor, the G-protein coupled receptor (GPCR) CXCR5, play fundamental roles in inflammatory, infectious and immune responses. Originally identified as a B-cell chemoattractant, CXCL13 exerts important functions in lymphoid neogenesis, and has been widely implicated in the pathogenesis of a number of autoimmune diseases and inflammatory conditions, as well as in lymphoproliferative disorders. Current evidence also indicates that the CXCL13:CXCR5 axis orchestrates cell-cell interactions that regulate lymphocyte infiltration within the tumor microenvironment, thereby determining responsiveness to cytotoxic and immune-targeted therapies. In this review, we provide a comprehensive perspective of the involvement of CXCL13 and its receptor in cancer progression. Studies in recent years postulated novel roles for this chemokine in controlling the cancer cell phenotype, and suggest important functions in the growth and metastatic dissemination of solid tumors. Carcinogens have been found to induce CXCL13 production, and production of this chemokine within the tumor milieu has been shown to impact the proliferation, migration, and invasive properties of cancer cells. Thus, the complex networks of cellular interactions involving tumoral CXCL13 and CXCR5 integrate to promote cancer cell autonomous and non-autonomous responses, highlighting the relevance of autocrine and paracrine interactions in dictating the cancer phenotype. Dissecting the molecular and signaling events regulated by CXCL13 and how this chemokine dynamically controls the interaction between the cancer cell and the tumor microenvironment is key to identify novel effectors and therapeutic targets for cancer treatment.

Role of ALDH1A1 and HTRA2 expression in CCL2/CCR2-mediated breast cancer cell growth and invasion

Chemokines mediate immune cell trafficking during tissue development, wound healing and infection. The chemokine CCL2 is best known to regulate macrophage recruitment during wound healing, infection and inflammatory diseases. While the importance of CCL2/CCR2 signaling in macrophages during cancer progression is well documented, we recently showed that CCL2-mediated breast cancer progression depends on CCR2 expression in carcinoma cells. Using 3D Matrigel: Collagen cultures of SUM225 and DCIS.com breast cancer cells, this study characterized the mechanisms of CCL2/CCR2 signaling in cell growth and invasion. SUM225 cells, which expressed lower levels of CCR2 than DCIS.com cells, formed symmetrical spheroids in Matrigel: Collagen, and were not responsive to CCL2 treatment. DCIS.com cells formed asymmetric cell clusters in Matrigel: Collagen. CCL2 treatment increased growth, decreased expression of E-cadherin and increased TWIST1 expression. CCR2 overexpression in SUM225 cells increased responsiveness to CCL2 treatment, enhancing growth and invasion. These phenotypes corresponded to increased expression of Aldehyde Dehydrogenase 1A1 (ALDH1A1) and decreased expression of the mitochondrial serine protease HTRA2. CCR2 deficiency in DCIS.com cells inhibited CCL2-mediated growth and invasion, corresponding to decreased ALDH1A1 expression and increased HTRA2 expression. ALDH1A1 and HTRA2 expression were modulated in CCR2-deficient and CCR2-overexpressing cell lines. We found that ALDH1A1 and HTRA2 regulates CCR2-mediated breast cancer cell growth and cellular invasion in a CCL2/CCR2 context-dependent manner. These data provide novel insight on the mechanisms of chemokine signaling in breast cancer cell growth and invasion, with important implications on targeted therapeutics for anti-cancer treatment.

This article has an associated First Person interview with the first author of the paper.

Summary: Chemokines are known to regulate immune cell recruitment during inflammation. This report characterizes novel molecular mechanisms through which CCL2/CCR2 chemokine signaling in breast cancer cells regulates growth and invasion.

Association analysis of the common varieties of IL17A and IL17F genes with the risk of knee osteoarthritis

Osteoarthritis is mediated by various types of cytokines, growth factors, and inflammatory factors that the role of the interleukin-17 family in this disease is becoming increasingly apparent. The aim of this study is to determine the association between the common polymorphisms of IL17A (including rs2275913) and IL17F (including rs2397084 and rs763780) genes with the knee osteoarthritis risk which was followed by a bioinformatics approach. In a case-control study, 254 participants consisting of 127 healthy individuals and 127 subjects with knee osteoarthritis referring to Shahid Beheshti Hospital dependents on Kashan University of Medical Sciences (Kashan, Iran) were enrolled. After samples collection, the polymorphisms genotyping was determined by the polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) method. Finally, some bioinformatics tools were used to analyze the molecular effects of the three studied polymorphisms. Data analysis showed a significant association between rs2275913-GA genotype and the decreased risk of knee osteoarthritis (OR = 0.57, 95% CI = 0.33-0.97, P = .040). However, rs763780-AG genotype (OR = 2.29, 95%CI = 1.11-4.69, P = .024) and rs763780-G allele (OR = 2.01, 95% CI = 1.09-3.72, P = .026) were associated with an increased risk of knee osteoarthritis. However, no significant associations were found between the rs2397084 polymorphism and knee osteoarthritis risk. Our structural analysis revealed that the rs2275913 polymorphism could create a new binding site for TFII-I at the promoter region of IL17A. Also, rs2397084 and rs763780 could significantly affect the function and structure of IL17A. Based on our findings, rs2275913 and rs763780 could be considered as protective and risk factors for knee osteoarthritis, respectively. Therefore, these polymorphisms can be considered as biomarkers for the screening of knee osteoarthritis susceptible persons.

Influence of Chemokine N-Terminal Modification on Biased Agonism at the Chemokine Receptor CCR1

Leukocyte migration, a hallmark of the inflammatory response, is stimulated by the interactions between chemokines, which are expressed in injured or infected tissues, and chemokine receptors, which are G protein-coupled receptors (GPCRs) expressed in the leukocyte plasma membrane. One mechanism for the regulation of chemokine receptor signaling is biased agonism, the ability of different chemokine ligands to preferentially activate different intracellular signaling pathways via the same receptor. To identify features of chemokines that give rise to biased agonism, we studied the activation of the receptor CCR1 by the chemokines CCL7, CCL8, and CCL15(Δ26). We found that, compared to CCL15(Δ26), CCL7 and CCL8 exhibited biased agonism towards cAMP inhibition and away from β-Arrestin 2 recruitment. Moreover, N-terminal substitution of the CCL15(Δ26) N-terminus with that of CCL7 resulted in a chimera with similar biased agonism to CCL7. Similarly, N-terminal truncation of CCL15(Δ26) also resulted in signaling bias between cAMP inhibition and β-Arrestin 2 recruitment signals. These results show that the interactions of the chemokine N-terminal region with the receptor transmembrane region play a key role in selecting receptor conformations coupled to specific signaling pathways.

Matrix metalloproteinase-9 deficiency protects mice from severe influenza A viral infection

Matrix metalloproteinase-9 (MMP-9) cleaves various proteins to regulate inflammatory and injury responses. However, MMP-9's activities during influenza A viral (IAV) infections are incompletely understood. Herein, plasma MMP-9 levels were increased in patients with pandemic H1N1 and seasonal IAV infections. MMP-9 lung levels were increased and localized to airway epithelial cells and leukocytes in H1N1-infected WT murine lungs. H1N1-infected Mmp-9-/- mice had lower mortality rates, reduced weight loss, lower lung viral titers, and reduced lung injury, along with lower E-cadherin shedding in bronchoalveolar lavage fluid (BALF) samples than WT mice. H1N1-infected Mmp-9-/- mice had an altered immune response to IAV with lower BALF PMN and macrophage counts, higher Th1-like CD4+ and CD8+ T cell subsets, lower T regulatory cell counts, reduced lung type I interferon levels, and higher lung interferon-γ levels. Mmp-9 bone marrow-chimera studies revealed that Mmp-9 deficiency in lung parenchymal cells protected mice from IAV-induced mortality. H1N1-infected Mmp-9-/- lung epithelial cells had lower viral titers than H1N1-infected WT cells in vitro. Thus, H1N1-infected Mmp-9-/- mice are protected from IAV-induced lung disease due to a more effective adaptive immune response to IAV and reduced epithelial barrier injury due partly to reduced E-cadherin shedding. Thus, we believe that MMP-9 is a novel therapeutic target for IAV infections.

Gelatinase B/matrix metalloproteinase-9 is a phase-specific effector molecule, independent from Fas, in experimental autoimmune encephalomyelitis

Gelatinase B/matrix metalloproteinase-9 (MMP-9) triggers multiple sclerosis (MS) and the animal model of experimental autoimmune encephalomyelitis (EAE) by the breakdown of the blood-brain barrier. Interestingly, MMP-9 is beneficial in systemic autoimmunity caused by Fas-deficiency. Fas-deficient (faslpr) and Fas-ligand-deficient mice are protected against EAE. We here investigated the interaction between Fas and MMP-9 in the setting of induction of EAE and compared short- and long-term effects. We provoked EAE with myelin oligodendrocyte glycoprotein (MOG) peptide and compared EAE development in four genotypes (wild-type (WT), single knockout mmp-9-/-, faslpr, and mmp-9-/-/faslpr) and monitored leukocytes, cytokines and chemokines as immunological parameters. As expected, faslpr mice were resistant against EAE induction, whereas MMP-9 single knockout mice were not. In the double mmp-9-/-/ faslpr mice the effects on disease scores pointed to independent rather than interrelated disease mechanisms. On a short term, after EAE induction leukocytes infiltrated into the brain and cytokine and chemokine levels were significantly higher in all the four genotypes studied, even in the faslpr and mmp-9-/-/faslpr, which did not develop clinical disease. The levels of MMP-9 but not of MMP-2 were increased in the brain and in the peripheral organs after EAE induction. After 40 days all the animals recovered and did not show signs of EAE. However, the absence of MMP-9 in the remission phase suggested a protective role of MMP-9 in the late phase of the disease, because single mmp-9-/- mice presented a delayed remission in comparison with WT animals suggesting a phase-dependent role of MMP-9 in the disease. Nevertheless, the levels of some cytokines and chemokines remained higher than in control animals even 100 days after EAE induction, attesting to a prolonged state of immune activation. We thus yielded new insights and useful markers to monitor this activated immune status. Furthermore, MMP-9 but not MMP-2 levels remained increased in the brains and, to a higher extend, in the spleens of the WT mice even during the remission phase, which is in line with the role of MMP-9 as a useful marker and a protective factor for EAE in the remission phase.

Interplay of DDP4 and IP-10 as a Potential Mechanism for Cell Recruitment to Tuberculosis Lesions

INTRODUCTION

Mycobacterium tuberculosis is one of the world's most successful pathogens equipped to establish itself within the human host as a subclinical infection without overt disease. Unable to eradicate the bacteria, the immune system contains the infection in a granuloma structure. Th1 cells that are essential for infection control are recruited to the site of infection directed by chemokines, predominantly CXCL10. It has previously been shown that CXCL10 in the plasma of patients chronically infected with hepatitis C virus is present primarily in an antagonist form. This is due to N-terminal truncation by the enzyme DPP4, which results in the antagonist form that is capable of binding its receptor CXCR3, but does not induce signaling. We aimed to explore whether such CXCL10 antagonism may have an impact on the pathogenesis of tuberculosis (TB).

RESULTS

We measured plasma levels of agonist and antagonist CXCL10 by Simoa digital ELISA, as well as DPP4 enzyme activity in the plasma of 20 patients with active TB infection, 10 patients with pneumonia infection, and a group of 10 healthy controls. We found higher levels of total and antagonist CXCL10 and reduced DPP4 enzyme activity in the plasma of TB patients compared to controls. We traced the source of CXCL10 secretion using immunohistochemical and confocal analysis to multinucleated giant cells in the TB lesions, and variable expression by macrophages. Interestingly, these cells were associated with DPP4-positive T cells. Moreover, the analysis of lymphocytes at the site of TB infection (bronchoalveolar lavage) showed a reduced frequency of CXCR3+ T cells.

INTERPRETATION

Our data suggests that CXCL10 antagonism may be an important regulatory mechanism occurring at the site of TB pathology. CXCL10 can be inactivated shortly after secretion by membrane bound DPP4 (CD26), therefore, reducing its chemotactic potential. Given the importance of Th1 cell functions and IFN-γ-mediated effects in TB, our data suggest a possible unappreciated regulatory role of DPP4 in TB.

PERSPECTIVES

DPP4 is the target for a class of enzyme inhibitors used in the treatment of diabetes, and the results from this study suggest that these drugs could be repurposed as an adjunct immunotherapy of patients with TB and MDR-TB.

Immunoregulatory Effects of Myeloid-Derived Suppressor Cell Exosomes in Mouse Model of Autoimmune Alopecia Areata

The treatment of autoimmune diseases still poses a major challenge, frequently relying on non-specific immunosuppressive drugs. Current efforts aim at reestablishing self tolerance using immune cells with suppressive activity like the regulatory T cells (Treg) or the myeloid-derived suppressor cells (MDSC). We have demonstrated therapeutic efficacy of MDSC in mouse Alopecia Areata (AA). In the same AA model, we now asked whether MDSC exosomes (MDSC-Exo) can replace MDSC. MDSC-Exo from bone marrow cells (BMC) cultures of healthy donors could substantially facilitate treatment. With knowledge on MDSC-Exo being limited, their suitability needs to be verified in advance. Protein marker profiles suggest comparability of BMC- to ex vivo collected inflammatory MDSC/MDSC-Exo in mice with a chronic contact dermatitis, which is a therapeutic option in AA. Proteome analyses substantiated a large overlap of function-relevant molecules in MDSC and MDSC-Exo. Furthermore, MDSC-Exo are taken up by T cells, macrophages, NK, and most avidly by Treg and MDSC-Exo uptake exceeds binding of MDSC themselves. In AA mice, MDSC-Exo preferentially target skin-draining lymph nodes and cells in the vicinity of remnant hair follicles. MDSC-Exo uptake is accompanied by a strong increase in Treg, reduced T helper proliferation, mitigated cytotoxic activity, and a slight increase in lymphocyte apoptosis. Repeated MDSC-Exo application in florid AA prevented progression and sufficed for partial hair regrowth. Deep sequencing of lymphocyte mRNA from these mice revealed a significant increase in immunoregulatory mRNA, including FoxP3 and arginase 1. Downregulated mRNA was preferentially engaged in prohibiting T cell hyperreactivity. Taken together, proteome analysis provided important insights into potential MDSC-Exo activities, these Exo preferentially homing into AA-affected organs. Most importantly, changes in leukocyte mRNA seen after treatment of AA mice with MDSC-Exo sustainably supports the strong impact on the adaptive and the non-adaptive immune system, with Treg expansion being a dominant feature. Thus, MDSC-Exo could potentially serve as therapeutic agents in treating AA and other autoimmune diseases.

Matrix Metalloproteinase-9-Generated COOH-, but Not NH2-Terminal Fragments of Serum Amyloid A1 Retain Potentiating Activity in Neutrophil Migration to CXCL8, With Loss of Direct Chemotactic and Cytokine-Inducing Capacity

Serum amyloid A1 (SAA1) is a prototypic acute phase protein, induced to extremely high levels by physical insults, including inflammation and infection. Human SAA and its NH₂-terminal part have been studied extensively in the context of amyloidosis. By contrast, little is known about COOH-terminal fragments of SAA. Intact SAA1 chemoattracts leukocytes via the G protein-coupled receptor formyl peptide receptor like 1/formyl peptide receptor 2 (FPR2). In addition to direct leukocyte activation, SAA1 induces chemokine production by signaling through toll-like receptor 2. We recently discovered that these induced chemokines synergize with intact SAA1 to chemoattract leukocytes in vitro and in vivo. Gelatinase B or matrix metalloproteinase-9 (MMP-9) is also induced by SAA1 during infection and inflammation and processes many substrates in the immune system. We demonstrate here that MMP-9 rapidly cleaves SAA1 at a known consensus sequence that is also present in gelatins. Processing of SAA1 by MMP-9 at an accessible loop between two alpha helices yielded predominantly three COOH-terminal fragments: SAA1(52–104), SAA1(57–104), and SAA1(58–104), with a relative molecular mass of 5,884.4, 5,327.3, and 5,256.3, respectively. To investigate the effect of proteolytic processing on the biological activity of SAA1, we chemically synthesized the COOH-terminal SAA fragments SAA1(52–104) and SAA1(58–104) and the complementary NH₂-terminal peptide SAA1(1–51). In contrast to intact SAA1, the synthesized SAA1 peptides did not induce interleukin-8/CXCL8 in monocytes or fibroblasts. Moreover, these fragments possessed no direct chemotactic activity for neutrophils, as observed for intact SAA1. However, comparable to intact SAA1, SAA1(58–104) cooperated with CXCL8 in neutrophil activation and migration, whereas SAA1(1–51) lacked this potentiating activity. This cooperative interaction between the COOH-terminal SAA1 fragment and CXCL8 in neutrophil chemotaxis was mediated by FPR2. Hence, proteolytic cleavage of SAA1 by MMP-9 fine tunes the inflammatory capacity of this acute phase protein in that only the synergistic interactions with chemokines remain to prolong the duration of inflammation.

The ectoenzyme-side of matrix metalloproteinases (MMPs) makes inflammation by serum amyloid A (SAA) and chemokines go round

During an inflammatory response, a large number of distinct mediators appears in the affected tissues or in the blood circulation. These include acute phase proteins such as serum amyloid A (SAA), cytokines and chemokines and proteolytic enzymes. Although these molecules are generated within a cascade sequence in specific body compartments allowing for independent action, their co-appearance in space and time during acute or chronic inflammation points toward important mutual interactions. Pathogen-associated molecular patterns lead to fast induction of the pro-inflammatory endogenous pyrogens, which are evoking the acute phase response. Interleukin-1, tumor necrosis factor-α and interferons simultaneously trigger different cell types, including leukocytes, endothelial cells and fibroblasts for tissue-specific or systemic production of chemokines and matrix metalloproteinases (MMPs). In addition, SAA induces chemokines and both stimulate secretion of MMPs from multiple cell types. As a consequence, these mediators may cooperate to enhance the inflammatory response. Indeed, SAA synergizes with chemokines to increase chemoattraction of monocytes and granulocytes. On the other hand, MMPs post-translationally modify chemokines and SAA to reduce their activity. Indeed, MMPs internally cleave SAA with loss of its cytokine-inducing and direct chemotactic potential whilst retaining its capacity to synergize with chemokines in leukocyte migration. Finally, MMPs truncate chemokines at their NH₂- or COOH-terminal end, resulting in reduced or enhanced chemotactic activity. Therefore, the complex interactions between chemokines, SAA and MMPs either maintain or dampen the inflammatory response.