A novel, NH2-terminal sequence-characterized human monokine possessing neutrophil chemotactic, skin-reactive, and granulocytosis-promoting activity

Characteristics and preliminary immune function of SRA5 in Lateolabrax maculatus

Scavenger receptors (SRs) are crucial for pattern recognition in the innate immune system. However, the role of Scavenger Receptors class A member 5 (SRA5) in the immunological response of bony fish to pathogen invasion remains unclear. This study identified and characterized the SRA5 of Lateolabrax maculatus (LmSRA5) from its transcriptome database. LmSRA5 has a 1494 bp open reading frame, encodes 497 amino acids, has a molecular weight of 55.01 kDa, and contains a collagen domain and a conserved Scavenger Receptor Cysteine-Rich domain. LmSRA5 exhibited high sequence similarity to previously reported SRA5 genes. LmSRA5 exhibited high sequence similarity to previously reported SRA5 genes. LmSRA5 is primarily localized in the cytoplasm, with its encoded proteins distributed in both the cytoplasm and the cell membrane. LmSRA5 was expressed in all tissues. The highest expression was observed in the pituitary gland, with significant levels in the stomach, intestines, liver, and kidney. LmSRA5 expression in the head kidney, spleen, blood, and intestines initially increased, then decreased following infection with Aeromonas veronii. The binding affinity of LmSRA5 for A. veronii was enhanced by increasing concentrations of the extracellular domain recombinant LmSRA5. Knockdown and overexpression experiments in liver cells demonstrated that LmSRA5 significantly regulates the expression of IL-8 and c-Jun. LmSRA5 participates in the immune response by recognizing pathogen-associated molecular patterns (PAMPs) and contributes to immune regulation through modulation IL-8 and c-Jun. This study offers valuable insights into the role of SRA5 in pathogen resistance and immune regulation in bony fish, thereby contributing to the advancement of aquaculture under escalating disease pressures.

The role of CXC chemokines and receptors in breast cancer

CXC chemokines are a class of cytokines possessing chemotactic properties. Studies indicate that CXC chemokines exhibit dysregulation in miscellaneous cancer categories and are significantly associated with the advancement of tumors. Breast cancer is a commonly diagnosed and fatal cancer among the female population. Breast cancer pathogenesis and progression involve various mechanisms, including invasion, metastasis, angiogenesis, and inflammation. Chemokines and their receptors are involved in all of these processes. The CXC chemokine receptors (CXCRs) and their related ligands have attracted considerable attention due to their multifaceted functions in facilitating and controlling tumor proliferation. CXCRs are expressed by both cancer cells and immune cells, and they play a crucial role in regulating the tumor microenvironment and the immune response. This review aims to assess the potential of CXCRs and CXC chemokines as therapeutic targets or biomarkers for personalized therapy. Additionally, it provides an overview of the current understanding of the expression, function, and prognostic relevance of CXCRs in breast cancer. Furthermore, the challenges and potential prospects pertaining to CXCR investigation in breast cancer are deliberated.

The Gastroprotective Effect of Sicyos angulatus Against Hydrochloric Acid/Ethanol-Induced Acute Gastritis and Gastric Ulcer in Mice

Gastritis and gastric ulcers are common gastric diseases that are caused by infection, drugs, alcohol consumption, or stress. These conditions lead to increased inflammatory cytokines and recruitment of leukocytes, which damage the stomach mucosa and exacerbate disease severity. Sicyos angulatus (SA), an annual vine in the Cucurbitaceae family, is known to have an anti-inflammatory effect, but its efficacy for preventing gastritis and gastric ulcers has not yet been evaluated. In the present study, we investigated the gastroprotective effect of SA using a hydrochloric acid/ethanol-induced gastric mucosal injury mouse model and lipopolysaccharide (LPS)-stimulated KATO III cells. Macroscopic analysis revealed a reduction in gastric ulcer area. Similarly, histopathological analysis showed a dose-dependent decrease in gastric mucosal injury, with significant improvement at 750 mg/kg of SA treatment. Gene expressions of inflammatory cytokines, chemokines, and adhesion molecule were reduced in the SA-administered group. Immunohistochemical staining indicated that SA significantly decreased neutrophil infiltration in the lamina propria and epithelium of the stomach. Kaempferol, a major bioactive flavonoid of SA, also improved gastric injury by reducing macroscopic and microscopic lesions, inflammatory mediator gene expression, and neutrophil infiltration. Furthermore, both SA and kaempferol downregulated LPS-mediated increases in inflammatory cytokines and chemokines following inhibition of p38 and c-Jun N-terminal kinase (JNK) phosphorylation in KATO III cells. These results suggest that SA can ameliorate gastric mucosal injury by inhibiting the recruitment of inflammatory cells, particularly neutrophils, and by suppressing p38 and JNK phosphorylation.

Neutrophil extracellular traps and neutrophil-related mediators in human thyroid cancer

Background

Polymorphonuclear neutrophils (PMNs) are the main effector cells in inflammatory responses and play multiple roles in thyroid cancer (TC). PMNs contain and release a plethora of mediators, including granular enzymes [e.g., myeloperoxidase (MPO), pentraxin-3 (PTX3) and matrix metalloproteinase-9 (MMP-9)], and neutrophil extracellular traps (NETs). The aim of this study was to evaluate NETs and neutrophil-derived mediators as possible biomarkers in TC patients.

Methods

20 patients with differentiated thyroid cancer (DTC), 26 patients with dedifferentiated thyroid cancer (De-DTC), 26 patients with multinodular goiter (MNG) and 22 healthy controls (HCs) were recruited. Serum concentrations of free DNA (dsDNA), nucleosomes, citrullinated histone H3 (CitH3) and MPO-DNA complexes were evaluated as NET biomarkers. Neutrophil-related mediators such as MPO, PTX3, MMP-9, CXCL8, and granulocyte-monocyte colony-stimulating factor (GM-CSF) were measured by ELISA.

Results

Serum levels of all four NET biomarkers were increased in DeDTC patients compared to HCs. CitH3 serum levels were selectively increased in both DeDTC and DTC patients compared to HCs and MNG patients. MPO-DNA complexes and nucleosomes were selectively increased only in DeDTC patients compared to HCs and MNG patients. Moreover, MPO-DNA complexes were selectively increased in DeDTC patients compared to DTC patients also. MPO circulating levels were selectively increased in the DeDTC patient subgroup compared to HCs. Circulating levels of PTX3, MMP-9 and GM-CSF were increased in DTC and DeDTC patients compared to HCs. Nucleosomes positively correlated with dsDNA, CitH3, MPO and CXCL8. MPO-DNA complexes positively correlated with dsDNA, CitH3, CXCL8, MPO and nucleosome levels. Moreover, three out of the four NET biomarkers (i.e., dsDNA, nucleosomes and MPO-DNA complexes) were increased in elderly patients compared to young patients and in patients with metastatic disease at diagnosis compared to non metastatic patients. Nucleosomes were higher in males compared to females.

Conclusion

MPO-DNA complexes, nucleosomes and, to some extent, CitH3 levels seem to correlate with malignancy and severity of progressive TC. Moreover, serum concentrations of PMN-related mediators (MPO, PTX3, GM-CSF) were increased in TCs compared to MNG and HCs.

Circulating interleukins and risk of colorectal cancer: a Mendelian randomization study

BACKGROUND

Recent studies have suggested a potential causal association between Interleukins (ILs) and Colorectal Cancer (CRC), and thus, it is important to examine the causal relationship between them using a Mendelian randomization (MR) approach.

METHODS

The instrumental variables were extracted for IL-1ra, IL-6, IL-6ra, IL-8, IL-16, IL-18, IL-27 from genome-wide association studies of European ancestry. Summary statistics of CRC were also retrieved. An inverse variance-weighted MR approach was implemented as the primary method to compute overall effects from multiple instruments. Additional MR approaches and sensitivity and heterogeneity pleiotropy analyses were also conducted respectively.

RESULTS

Our analysis suggested a causal effect between an increase of IL-8 and a reduced risk of CRC (odds ratio 0.65; 95% confidence interval, 0.43-0.98; p = 0.041) and did not provide evidence for causal effects of IL-1ra, IL-6, IL-6ra, IL-16, IL-18, IL-27. Sensitivity analyses suggested the robustness of MR results and that they were unlikely to be affected by unbalanced pleiotropy or significant heterogeneity.

CONCLUSIONS

This study investigated the role of ILs in the development of CRC and we found a causal effect between an increase of IL-8 and a reduced risk of CRC but not found evidence for causal effects of IL-1ra, IL-6, IL-6ra, IL-16, IL-18, IL-27. Sensitivity analyses suggested the robustness of MR results and that they were unlikely to be affected by unbalanced pleiotropy or significant heterogeneity.

Interleukins 20 and 8 - less widely known cytokines in psoriasis

Psoriasis is a common immune-mediated inflammatory dermatosis affecting 2-3% of the northern European population. Although its aetiology is not completely elucidated, it is widely accepted that activated immune cells and keratinocytes stimulate keratinocyte hyperproliferation by production of cytokines; indeed, elevated amounts of pro-inflammatory cytokines have been observed in skin lesions and patient serum. By identifying those playing a central role in the disease pathogenesis, it will be possible to indicate a potential therapeutic target. Drugs targeting tumour necrosis factor α (TNF-α), interleukin (IL)-12/23, IL-17, IL-22 and IL-23 and Janus kinase inhibitors have been found to successfully alleviate resistant skin lesions. However, psoriasis is a complex disease with varied cellular interactions and cytokines, and a complex receptor network. Therefore, this review paper examines the less widely known cytokines IL-20 and IL-8, their therapeutic potential and their role in skin lesion development. Although promising results have been obtained for IL-20 and IL-8 treatment, and their role in the psoriasis skin lesion development is well documented, the role of these two cytokines remains overshadowed by that of the wider systemic cytokine storm.

Role of Defensins in Tumor Biology

Defensins have long been considered as merely antimicrobial peptides. Throughout the years, more immune-related functions have been discovered for both the α-defensin and β-defensin subfamily. This review provides insights into the role of defensins in tumor immunity. Since defensins are present and differentially expressed in certain cancer types, researchers started to unravel their role in the tumor microenvironment. The human neutrophil peptides have been demonstrated to be directly oncolytic by permealizing the cell membrane. Further, defensins can inflict DNA damage and induce apoptosis of tumor cells. In the tumor microenvironment, defensins can act as chemoattractants for subsets of immune cells, such as T cells, immature dendritic cells, monocytes and mast cells. Additionally, by activating the targeted leukocytes, defensins generate pro-inflammatory signals. Moreover, immuno-adjuvant effects have been reported in a variety of models. Therefore, the action of defensins reaches beyond their direct antimicrobial effect, i.e., the lysis of microbes invading the mucosal surfaces. By causing an increase in pro-inflammatory signaling events, cell lysis (generating antigens) and attraction and activation of antigen presenting cells, defensins could have a relevant role in activating the adaptive immune system and generating anti-tumor immunity, and could thus contribute to the success of immune therapy.

The chemokines CXCL8 and CXCL12: molecular and functional properties, role in disease and efforts towards pharmacological intervention

Chemokines are an indispensable component of our immune system through the regulation of directional migration and activation of leukocytes. CXCL8 is the most potent human neutrophil-attracting chemokine and plays crucial roles in the response to infection and tissue injury. CXCL8 activity inherently depends on interaction with the human CXC chemokine receptors CXCR1 and CXCR2, the atypical chemokine receptor ACKR1, and glycosaminoglycans. Furthermore, (hetero)dimerization and tight regulation of transcription and translation, as well as post-translational modifications further fine-tune the spatial and temporal activity of CXCL8 in the context of inflammatory diseases and cancer. The CXCL8 interaction with receptors and glycosaminoglycans is therefore a promising target for therapy, as illustrated by multiple ongoing clinical trials. CXCL8-mediated neutrophil mobilization to blood is directly opposed by CXCL12, which retains leukocytes in bone marrow. CXCL12 is primarily a homeostatic chemokine that induces migration and activation of hematopoietic progenitor cells, endothelial cells, and several leukocytes through interaction with CXCR4, ACKR1, and ACKR3. Thereby, it is an essential player in the regulation of embryogenesis, hematopoiesis, and angiogenesis. However, CXCL12 can also exert inflammatory functions, as illustrated by its pivotal role in a growing list of pathologies and its synergy with CXCL8 and other chemokines to induce leukocyte chemotaxis. Here, we review the plethora of information on the CXCL8 structure, interaction with receptors and glycosaminoglycans, different levels of activity regulation, role in homeostasis and disease, and therapeutic prospects. Finally, we discuss recent research on CXCL12 biochemistry and biology and its role in pathology and pharmacology.

CXCR1/2 dual-inhibitor ladarixin reduces tumour burden and promotes immunotherapy response in pancreatic cancer

BACKGROUND

Pancreatic ductal adenocarcinoma (PDAC) is a highly lethal malignancy with few therapeutic options available. Despite immunotherapy has revolutionised cancer treatment, the results obtained in PDAC are still disappointing. Emerging evidence suggests that chemokines/CXCRs-axis plays a pivotal role in immune tumour microenvironment modulation, which may influence immunotherapy responsiveness. Here, we evaluated the effectiveness of CXCR1/2 inhibitor ladarixin, alone or in combination with anti-PD-1, against immunosuppression in PDAC.

METHODS

A set of preclinical models was obtained by engrafting mouse PDAC-derived cells into syngeneic immune-competent mice, as well as by orthotopically transplanting patient-derived PDAC tumour into human immune-system-reconstituted (HIR) mice (HuCD34-NSG-mice). Tumour-bearing mice were randomly assigned to receive vehicles, ladarixin, anti-PD-1 or drugs combination.

RESULTS

CXCR1/2 inhibition by ladarixin reverted in vitro tumour-mediated M2 macrophages polarisation and migration. Ladarixin as single agent reduced tumour burden in cancer-derived graft (CDG) models with high-immunogenic potential and increased the efficacy of ICI in non-immunogenic CDG-resistant models. In a HIR mouse model bearing the immunogenic subtype of human PDAC, ladarixin showed high efficacy increasing the antitumor effect of anti-PD-1.

CONCLUSION

Ladarixin in combination with anti-PD-1 might represent an extremely effective approach for the treatment of immunotherapy refractory PDAC, allowing pro-tumoral to immune-permissive microenvironment conversion.

Thirty-five years since the discovery of chemotactic cytokines, interleukin-8 and MCAF: A historical overview

Inflammation is a host defense response to various invading stimuli, but an excessive and persistent inflammatory response can cause tissue injury, which can lead to irreversible organ damage and dysfunction. Excessive inflammatory responses are believed to link to most human diseases. A specific type of leukocyte infiltration into invaded tissues is required for inflammation. Historically, the underlying molecular mechanisms of this process during inflammation were an enigma, compromising research in the fields of inflammation, immunology, and pathology. However, the pioneering discovery of chemotactic cytokines (chemokines), monocyte-derived neutrophil chemotactic factor (MDNCF; interleukin [IL]-8, CXCL8) and monocyte chemotactic and activating factor (MCAF; monocyte chemotactic factor 1 [MCP-1], CCL2) in the late 1980s finally enabled us to address this issue. In this review, we provide a historical overview of chemokine research over the last 35 years.

No NETs no TIME: Crosstalk between neutrophil extracellular traps and the tumor immune microenvironment

The tumor immune microenvironment (TIME) controls tumorigenesis. Neutrophils are important components of TIME and control tumor progression and therapy resistance. Neutrophil extracellular traps (NETs) ejected by activated neutrophils are net-like structures composed of decondensed extracellular chromatin filaments decorated with a plethora of granules as well as cytoplasmic proteins. Many of these harbour post translational modifications. Cancer cells reportedly trigger NET formation, and conversely, NETs alter the TIME and promote tumor cell proliferation and migration. The specific interactions between NETs and TIME and the respective effects on tumor progression are still elusive. In certain tumors, a CD4+ T helper (Th) 2 cell-associated TIME induces NETs and exerts immunosuppressive functions via programmed death 1 (PD-1)/PD-L1, both associated with poorer prognosis. In other cases, NETs induce the proliferation of Th1 cells, associated with an improved prognosis in cancer. In addition, NETs can drive macrophage polarization and often rely on macrophages to promote cancer cell invasion and metastasis. In turn, macrophages can swiftly clear NETs in an immunologically silent manner. The aim of this review is to summarize the knowledge about the mutual interaction between NETs and TIME and its impact on tumor growth and therapy.

How to place the duality of specific MMP-9 inhibition for treatment of inflammatory bowel diseases into clinical opportunities?

Crohn’s disease (CD) and ulcerative colitis (UC) are inflammatory bowel diseases (IBD) with the involvement of immune cells and molecules, including cytokines, chemokines and proteases. A previous extensive review about the molecular biology of matrix metalloproteases (MMPs) and tissue inhibitors of metalloproteases (TIMPs), related to intestinal barrier destruction and restoration functions in IBD, is here complemented with the literature from the last five years. We also compare IBD as a prototypic mucosal inflammation of an epithelial barrier against microorganisms with inflammatory retinopathy as a disease with a barrier dysfunction at the level of blood vessels. Multiple reasons are at the basis of halting clinical trials with monoclonal antibodies against MMP-9 for IBD treatment. These include (i) the absence of a causative role of MMP-9 in the pathology in animal models of IBD, (ii) the fact that endotoxins, crossing the intestinal barrier, induce massive local release of both neutrophil collagenase (MMP-8) and gelatinase B (MMP-9), (iii) insufficient recognition that MMPs modify the activities of cytokines, chemokines and their receptors, (iv) ignorance that MMPs exist as mixtures of proteoforms with different posttranslational modifications and with different specific activities and (v) the fact that MMPs and TIMPs act in an interactive network, possibly having also beneficial effects on IBD evolution. Nevertheless, inhibition of MMPs may be a useful therapeutic approach during specific IBD disease phases or in specific sub-phenotypes. This temporary “window of opportunity” for MMP-9 inhibition may be complemented by a locoregional one, provided that the pharmacological agents are targeted in time to affected tissues, as is achieved in ophthalmological inflammation. Thus, in order to discover spatial and temporal windows of opportunity for MMP inhibition as treatment of IBD, more preclinical work including well controlled animal studies will be further needed. In this respect, MMP-9/NGAL complex analysis in various body compartments is helpful for better stratification of IBD patients who may benefit from anti-MMP-9.

A Therapeutically Actionable Protumoral Axis of Cytokines Involving IL-8, TNFα, and IL-1β

Interleukin-8 (CXCL8) produced in the tumor microenvironment correlates with poor response to checkpoint inhibitors and is known to chemoattract and activate immunosuppressive myeloid leukocytes. In human cancer, IL8 mRNA levels correlate with IL1B and TNF transcripts. Both cytokines induced IL-8 functional expression from a broad variety of human cancer cell lines, primary colon carcinoma organoids, and fresh human tumor explants. Although IL8 is absent from the mouse genome, a similar murine axis in which TNFα and IL-1β upregulate CXCL1 and CXCL2 in tumor cells was revealed. Furthermore, intratumoral injection of TNFα and IL-1β induced IL-8 release from human malignant cells xenografted in immunodeficient mice. In all these cases, the clinically used TNFα blockers infliximab and etanercept or the IL-1β inhibitor anakinra was able to interfere with this pathogenic cytokine loop. Finally, in paired plasma samples of patients with cancer undergoing TNFα blockade with infliximab in a clinical trial, reductions of circulating IL-8 were substantiated.

SIGNIFICANCE

IL-8 attracts immunosuppressive protumor myeloid cells to the tumor microenvironment, and IL-8 levels correlate with poor response to checkpoint inhibitors. TNFα and IL-1β are identified as major inducers of IL-8 expression on malignant cells across cancer types and models in a manner that is druggable with clinically available neutralizing agents. This article is highlighted in the In This Issue feature, p. 2007.

Atypical response to bacterial co-infection and persistent neutrophilic broncho-alveolar inflammation distinguish critical COVID-19 from influenza

Neutrophils are recognized as important circulating effector cells in the pathophysiology of severe coronavirus disease 2019 (COVID-19). However, their role within the inflamed lungs is incompletely understood. Here, we collected broncho-alveolar lavage (BAL) fluids and parallel blood samples of critically ill COVID-19 patients requiring invasive mechanical ventilation and compared BAL fluid parameters with those of mechanically ventilated influenza patients, as a non-COVID-19 viral pneumonia cohort. Compared to influenza, BAL fluids of COVID-19 patients contained increased numbers of hyperactivated degranulating neutrophils and elevated concentrations of the cytokines IL-1β, IL-1RA, IL-17A, TNF-α and G-CSF, the chemokines CCL7, CXCL1, CXCL8, CXCL11 and CXCL12α, and the protease inhibitors elafin, secretory leukocyte protease inhibitor (SLPI) and tissue inhibitor of metalloproteinases 1 (TIMP-1). In contrast, α-1 antitrypsin levels and net proteolytic activity were comparable in COVID-19 and influenza BAL fluids. During antibiotics treatment for bacterial co-infections, increased BAL fluid levels of several activating and chemotactic factors for monocytes, lymphocytes and NK cells were detected in COVID-19 patients whereas concentrations tended to decrease in influenza patients, highlighting the persistent immunological response to co-infections in COVID-19. Finally, the high proteolytic activity in COVID-19 lungs suggests considering protease inhibitors as a treatment option.

A highly efficient method for the production and purification of recombinant human CXCL8

Chemokines play diverse and fundamental roles in the immune system and human disease, which has prompted their structural and functional characterisation. Production of recombinant chemokines that are folded and bioactive is vital to their study but is limited by the stringent requirements of a native N-terminus for receptor activation and correct disulphide bonding required to stabilise the chemokine fold. Even when expressed as fusion proteins, overexpression of chemokines in E. coli tends to result in the formation of inclusion bodies, generating the additional steps of solubilisation and refolding. Here we present a novel method for producing soluble chemokines in relatively large amounts via a simple two-step purification procedure with no requirements for refolding. CXCL8 produced by this method has the correct chemokine fold as determined by NMR spectroscopy and in chemotaxis assays was indistinguishable from commercially available chemokines. We believe that this protocol significantly streamlines the generation of recombinant chemokines.

Differential Interleukin-8 thresholds for chemotaxis and netosis in human neutrophils

In humans, IL-8 (CXCL8) is a key chemokine for chemotaxis of polymorphonuclear leukocytes and monocytes/macrophages when acting on CXCR1 and CXCR2. CXCL8 activity on neutrophils includes chemotaxis and eliciting the extrusion of neutrophil extracellular traps (NETs). In this study, we show that concentrations of IL-8 that induce NETosis surpass in at least one order of magnitude those required to elicit chemoattraction in human neutrophils. IL-8-induced NETosis was less dependent on G-proteins than migration, while extracellular Ca⁺² chelation similarly inhibited both processes. Reactive oxygen species (ROS) were more important for NETosis than for chemotaxis as evidenced by neutralization with N-acetyl -cysteine. Interestingly, selective blockade with anti-CXCR1 mAb inhibited NETosis much more readily than chemotaxis, while pharmacological inhibition of both CXCR1 and CXCR2, or selective inhibition for CXCR2 alone, similarly inhibited both functions. Together, these results propose a model according to which low concentrations of IL-8 in a gradient attract neutrophils to the inflammatory foci, while high receptor-saturating concentrations of IL-8 give rise to NETosis once leukocytes reach the core of the inflammatory insult.

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.

Interferons and other cytokines, genetics and beyond in COVID-19 and autoimmunity

Interferons are the best antiviral agents in vitro against SARS-CoV-2 so far and genetic defects in their signaling cascade or neutralization of alfa-interferons by autoantibodies come with more severe COVID-19. However, there is more, as the SARS-CoV-2 dysregulates not only innate immune mechanisms but also T and B cell repertoires. Most genetic, hematological and immunological studies in COVID-19 are at present phenomenological. However, these and antecedent studies contain the seed grains to resolve many unanswered questions and a whole range of testable hypotheses. What are the links, if existing, between genetics and the occurrence of interferon-neutralizing antibodies? Are NAGGED (neutralizing and generated by gene defect) antibodies involved or not? Is the autoimmune process cause or consequence of virus infection? What are the roles played by cytokine posttranslational modifications, such as proteolysis, glycosylation, citrullination and others? How is systemic autoimmunity linked with type 1 interferons? These questions place cytokines and growth factors at pole positions as keys to unlock basic mechanisms of infection and (auto)immunity. Related to cytokine research, (1) COVID-19 patients develop neutralizing autoantibodies, mainly against alpha interferons and it is not yet established whether this is the consequence or cause of virus replication. (2) The glycosylation of recombinant interferon-beta protects against breaking tolerance and the development of neutralizing antibodies. (3) SARS-CoV-2 induces severe inflammation and release of extracellular proteases leading to remnant epitopes, e.g. of cytokines. (4) In the rare event of homozygous cytokine gene segment deletions, observed neutralizing antibodies may be named NAGGED antibodies. (5) Severe cytolysis releases intracellular content into the extracellular milieu and leads to regulated degradation of intracellular proteins and selection of antibody repertoires, similar to those observed in patients with systemic lupus erythematosus. (6) Systematic studies of novel autoimmune diseases on single cytokines will complement the present picture about interferons. (7) Interferon neutralization in COVID-19 constitutes a preamble of more studies about cytokine-regulated proteolysis in the control of autoimmunity. Here we reformulate these seven conjectures into testable questions for future research.

Interleukin-8 Levels in the Stratum Corneum as a Biomarker for Monitoring Therapeutic Effect in Atopic Dermatitis Patients

INTRODUCTION

The stratum corneum contains several growth factors and cytokines that are synthesized in keratinocytes. We previously reported that the amount of interleukin-8 in the stratum corneum (scIL-8) is related to the severity of local skin inflammation in atopic dermatitis (AD). However, it is unknown whether scIL-8 levels reflect pharmacologic responses to a therapeutic intervention in AD patients. Therefore, in this study, we aimed to investigate whether the improvement of dermatitis in AD is correlated with scIL-8 levels before and after topical corticosteroid treatment.

METHODS

Stratum corneum samples were collected from 22 AD patients using the noninvasive tape-stripping method before treatment, 2 weeks after topical treatment, and 4-6 weeks after treatment.

RESULTS

scIL-8 levels on the forearm reduced significantly from 790 ± 348 pg/mg before treatment to 163 ± 68 pg/mg 2 weeks after treatment and 100 ± 37 pg/mg 4-6 weeks after corticosteroid treatment. scIL-8 levels on the abdomen also reduced significantly from 902 ± 391 to 142 ± 38 pg/mg at the end of study. The reduction in scIL-8 levels was associated with the improvement in local skin severity in AD. We also found that scIL-8 levels, along with blood biomarker levels (serum thymus and activation-regulated chemokine, lactate dehydrogenase, and %eosinophil), decreased significantly after the treatment.

CONCLUSION

The scIL-8 concentration decreases with improvements in skin symptoms in AD patients after topical corticosteroid treatment; thus, it may be a suitable biomarker for monitoring therapeutic effects in AD patients.

IL8, Neutrophils, and NETs in a Collusion against Cancer Immunity and Immunotherapy

One of the most important mechanisms by which cancer fosters its own development is the generation of an immune microenvironment that inhibits or impairs antitumor immune responses. A cancer permissive immune microenvironment is present in a large proportion of the patients with cancer who do not respond to immunotherapy approaches intended to trigger preexisting antitumor immune responses, for instance, immune checkpoint blockade. High circulating levels of IL8 in patients with cancer quite accurately predict those who will not benefit from checkpoint-based immunotherapy. IL8 has been reported to favor cancer progression and metastases via different mechanisms, including proangiogenesis and the maintenance of cancer stem cells, but its ability to attract and functionally modulate neutrophils and macrophages is arguably one of the most important factors. IL8 does not only recruit neutrophils to tumor lesions, but also triggers the extrusion of neutrophil extracellular traps (NET). The relevance and mechanisms underlying the contribution of both neutrophils and NETs to cancer development and progression are starting to be uncovered and include both direct effects on cancer cells and changes in the tumor microenvironment, such as facilitating metastasis, awakening micrometastases from dormancy, and facilitating escape from cytotoxic immune cells. Blockade of IL8 or its receptors (CXCR1 and CXCR2) is being pursued in drug development, and clinical trials alone or in combination with anti-PD-L1 checkpoint inhibitors are already ongoing.

Comprehensive analysis of the prognostic value and immune function of chemokine-CXC receptor family members in breast cancer

Recently, immune checkpoint inhibitors (ICIs) have been successfully used for treating melanoma. Unfortunately, many breast cancer (BC) patients show low response to ICIs due to the lack of infiltrating immune cells. Previous studies revealed that chemokine-CXC receptors (CXCRs) play a crucial role in leukocyte infiltration and promote cancer cell proliferation, migration, metastasis, and angiogenesis. However, the underlying functions of CXCRs in cancer-immunity cycle remain unclear. In this study, we firstly found that in comparison to normal tissues, BC tissues, especially basal-like BC, showed increased mRNA levels of CXCR3/4/5/6/8, but decreased CXCR1/2/7 expression using UALCAN and TIMER database. Interestingly, it's was found that the mRNA levels of CXCR3/4/5/6 were decreased in lymphocyte depleted of the BC immune subtype. Subsequently, functional enrichment analysis of distinct CXCRs indicated that CXCR3/4/5/6 were strongly associated to immune-related biological functions. Therefore, further analysis using TIMER and TISIDB database suggested that CXCR3/4/5/6 expression were strongly correlated with tumor-infiltrating lymphocytes (TILs) and immune checkpoints in BC. Finally, Kaplan-Meier Plotter analysis indicated that high mRNA expression of CXCR4 predicted worse relapse-free survival (RFS), whereas CXCR3/5/6 indicated better RFS in BC patients. These findings suggest a therapeutic value for CXCR3/4/5/6 in combination with ICIs for the treatment of BC.

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.

Remnant Epitopes Generating Autoimmunity: From Model to Useful Paradigm

Autoimmune diseases are defined as pathologies of adaptive immunity by the presence of autoantibodies or MHC-restricted autoantigen-reactive T cells. Because autoreactivity is a normal process based on mechanisms producing repertoires of antibodies and T cell receptors, crucial questions about disease mechanisms and key steps for interference have been outstanding. We defined 25 years ago the 'remnant epitopes generate autoimmunity' (REGA)-model in which extracellular proteases from innate immune cells generate autoantigens. Here, we refine the REGA-model, tested in diseases ranging from organ-specific autoimmune diseases to systemic lupus erythematosus. It now constitutes a paradigm in which remnant epitopes generate, maintain, and regulate autoimmunity; are dependent on genetic and epigenetic influences; are produced in a disease phase-specific manner; and have therapeutic implications when targeted.

The significance of chemokine CXCL-8 in esophageal carcinoma

Chemokines are a group of small molecular weight proteins that are structurally related. These molecules play an important role in the growth, differentiation and activation of many types of cells [1, 2]. Chemokines are synthesized mostly by leukocytes and act through their cognate G-protein coupled receptors to cause a cellular response, such as migration, adhesion or chemotaxis [1, 3]. The chemokine family has been classified into four classes: CC, CXC, CX3C, and (X), based on the arrangement of N-terminal cysteine residues [4]. These small peptides may also be grouped into inflammatory, homeostatic or dual function chemokines. Inflammatory chemokines can be induced during an immune response, whereas homeostatic chemokines are involved in control of cell migration [5]. The chemokine receptors are seven-transmembrane receptors coupled to G-proteins, that consist of an N-terminus outside the cell surface, three extracellular and three intracellular loops as well as a C-terminus in the cytoplasm [6, 7].

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.

Angiodrastic Chemokines in Colorectal Cancer: Clinicopathological Correlations

Aim

To study the expression of angiodrastic chemokines in colorectal tumors and correlate findings with clinicopathological parameters and survival.

Methods

The proangiogenic factor VEGF, the angiogenic chemokines CXCL8 and CXCL6, and the angiostatic chemokine CXCL4 were measured by ELISA in tumor and normal tissue of 35 stage II and III patients and correlated with the histopathology markers Ki67, p53, p21, bcl2, EGFR, and MLH1 and 5-year survival. The Wilcoxon and chi-square tests were used for statistical comparisons.

Results

There was a significant increase of CXCL6 (p = 0.005) and VEGF (p = 0.003) in cancerous tissue compared to normal. Patients with lower levels of CXCL8 and CXCL4 lived significantly longer. Patients with loss of EGFR expression had higher levels of CXCL8 while p21 loss was associated with higher levels of CXCL6. Chemokine levels were not correlated with TNM or Dukes classification. Strong expression of p53 was accompanied by decreased survival.

Conclusions

(1) The angiogenic factors CXCL6 and VEGF are increased in colorectal cancer tissue with no association with the clinical stage of the disease or survival. (2) However, increased levels of tissue CXCL8 and CXCL4 are associated with poor survival. (3) Strong expression of p53 is found in patients with poor survival.

Immunomodulation as Rescue for Chronic Atonic Skin Wounds

Chronic skin wounds, caused by arterial or venous insufficiency or by physical pressure, constitute an increasing medical problem as populations age. Whereas typical wounds are characterized by local inflammation that participates in the healing process, atonic wounds lack inflammatory markers, such as neutrophil infiltration, and generally do not heal. Recently, prominent roles in the immunopathology of chronic wounds were attributed to dysregulations in specific cytokines, chemokines, matrix metalloproteinases (MMPs), and their substrates. Together with the complement system, these molecular players provide necessary defense against infections, initiate angiogenesis, and prepare tissue reconstitution. Here, we review the current state of the field and include the concept that, aside from surgery and stem cell therapy, healing may be enhanced by immunomodulating agents.

Neutrophils: Beneficial and Harmful Cells in Septic Arthritis

Septic arthritis is an inflammatory joint disease that is induced by pathogens such as Staphylococcus aureus. Infection of the joint triggers an acute inflammatory response directed by inflammatory mediators including microbial danger signals and cytokines and is accompanied by an influx of leukocytes. The recruitment of these inflammatory cells depends on gradients of chemoattractants including formylated peptides from the infectious agent or dying cells, host-derived leukotrienes, complement proteins and chemokines. Neutrophils are of major importance and play a dual role in the pathogenesis of septic arthritis. On the one hand, these leukocytes are indispensable in the first-line defense to kill invading pathogens in the early stage of disease. However, on the other hand, neutrophils act as mediators of tissue destruction. Since the elimination of inflammatory neutrophils from the site of inflammation is a prerequisite for resolution of the acute inflammatory response, the prolonged stay of these leukocytes at the inflammatory site can lead to irreversible damage to the infected joint, which is known as an important complication in septic arthritis patients. Thus, timely reduction of the recruitment of inflammatory neutrophils to infected joints may be an efficient therapy to reduce tissue damage in septic arthritis.

Chemoattractants and cytokines in primary ciliary dyskinesia and cystic fibrosis: key players in chronic respiratory diseases

Patients with primary ciliary dyskinesia (PCD) and cystic fibrosis (CF), two inherited disorders, suffer from recurrent airway infections characterized by persistent bacterial colonization and uncontrollable inflammation. Although present in high counts, neutrophils fail to clear infection in the airways. High levels of C-X-C motif chemokine ligand 8/interleukin-8 (CXCL8/IL-8), the most potent chemokine to attract neutrophils to sites of infection, are detected in the sputum of both patient groups and might cause the high neutrophil influx in the airways. Furthermore, in CF, airway neutrophils are highly activated because of the genetic defect and the high levels of proinflammatory chemoattractants and cytokines (e.g., CXCL8/IL-8, tumor necrosis factor-α and IL-17). The overactive state of neutrophils leads to lung damage and fuels the vicious circle of infection, excessive inflammation and tissue damage. The inflammatory process in CF airways is well characterized, whereas the lung pathology in PCD is far less studied. The knowledge of CF lung pathology could be useful to guide molecular investigations of the inflammatory processes in PCD lungs. Current available therapies can not completely remedy the chronic airway infections in these diseases. This review gives an overview of the role that chemoattractants and cytokines play in these neutrophil-dominated lung pathologies. Finally, the most frequently applied treatments in CF and PCD and new experimental therapies to reduce neutrophil-dominated airway inflammation are described.

Neutrophils from Patients with Primary Ciliary Dyskinesia Display Reduced Chemotaxis to CXCR2 Ligands

Primary ciliary dyskinesia (PCD), cystic fibrosis (CF), and chronic obstructive airway disease are characterized by neutrophilic inflammation in the lungs. In CF and chronic obstructive airway disease, improper functioning of neutrophils has been demonstrated. We hypothesized that the pulmonary damage in PCD might be aggravated by abnormal functioning neutrophils either as a primary consequence of the PCD mutation or secondary to chronic inflammation. We analyzed chemotactic responses and chemoattractant receptor expression profiles of peripheral blood neutrophils from 36 patients with PCD, 21 healthy children and 19 healthy adults. We stimulated peripheral blood monocytes from patients and healthy controls and measured CXCL8 and IL-1β production with ELISA. PCD neutrophils displayed reduced migration toward CXCR2 ligands (CXCL5 and CXCL8) in the shape change, microchamber and microslide chemotaxis assays, whereas leukotriene B4 and complement component 5a chemotactic responses were not significantly different. The reduced response to CXCL8 was observed in all subgroups of patients with PCD (displaying either normal ultrastructure, dynein abnormalities or central pair deficiencies) and correlated with lung function. CXCR2 was downregulated in about 65% of the PCD patients, suggestive for additional mechanisms causing CXCR2 impairment. After treatment with the TLR ligands lipopolysaccharide and peptidoglycan, PCD monocytes produced more CXCL8 and IL-1β compared to controls. Moreover, PCD monocytes also responded stronger to IL-1β stimulation in terms of CXCL8 production. In conclusion, we revealed a potential link between CXCR2 and its ligand CXCL8 and the pathogenesis of PCD.

Combined Stimulation with Interleukin-18 and Interleukin-12 Potently Induces Interleukin-8 Production by Natural Killer Cells

The combination of interleukin (IL)-18 and IL-12 (IL-18+IL-12) potently stimulates natural killer (NK) cells, triggering an innate immune response to infections and cancers. Strategies exploiting the effects of IL-18+IL-12 have shown promise for cancer immunotherapy. However, studies have primarily characterized the NK cell response to IL-18+IL-12 in terms of interferon (IFN)-γ production, with little focus on other cytokines produced. IL-8 plays a critical role in activating and recruiting immune cells, but it also has tumor-promoting functions. IL-8 is classically produced by regulatory NK cells; however, cytotoxic NK cells do not typically produce IL-8. In this study, we uncover that stimulation with IL-18+IL-12 induces high levels of IL-8 production by ex vivo expanded and freshly isolated NK cells and NK cells in peripheral blood mononuclear cells. We further report that tumor necrosis factor (TNF)-α, produced by NK cells following IL-18+IL-12 stimulation, regulates IL-8 production. The IL-8 produced is in turn required for maximal IFN-γ and TNF-α production. These findings may have important implications for the immune response to infections and cancer immunotherapies. This study broadens our understanding of NK cell function and IL-18+IL-12 synergy by uncovering an unprecedented ability of IL-18+IL-12-activated peripheral blood NK cells to produce elevated levels of IL-8 and identifying the requirement for intermediates induced by IL-18+IL-12 for maximal cytokine production following stimulation.

Neutrophils in ulcerative colitis: a review of selected biomarkers and their potential therapeutic implications

OBJECTIVES

This review article describes the role of neutrophils in mucosal injury and the resulting crypt abscesses characteristic of ulcerative colitis. We also review selected biomarkers for monitoring neutrophil presence and activity in the mucosa as well as their potential as therapeutic targets.

MATERIAL

We have collated and selectively reviewed data on the most prominent well-established and emerging neutrophil-related biomarkers and potential therapeutic targets (calprotectin, lactoferrin, CXCR1, CXCR2, MMP-9, NGAL, elafin, HNE, pANCAs, MPO, CD16, CD177, CD64, HNPs, SLPI and PTX3) in ulcerative colitis.

RESULTS

Systemic and intestinal neutrophil activity increases substantially in active ulcerative colitis, driving tissue damage and extra-intestinal manifestations. Calprotectin is a robust neutrophil and disease biomarker, and a few neutrophil-related targets are being clinically explored as therapeutic targets.

CONCLUSION

We propose that targeting neutrophils and their inflammatory mediators per se is an opportunity that should be explored to identify new effective medical therapies. The overall clinical goal for neutrophil-targeted therapy will be to modulate, but not completely silence, neutrophil activity, thereby abolishing the destructive inflammation with associated acute and chronic tissue damage without compromising host-defense.

Exosomes derived from human menstrual blood-derived stem cells alleviate fulminant hepatic failure

Background

Human menstrual blood-derived stem cells (MenSCs) are a novel source of MSCs that provide the advantage of being easy to collect and isolate. Exosomes contain some mRNAs and adhesion molecules that can potentially impact cellular and animal physiology. This study aimed to investigate the therapeutic potential of MenSC-derived exosomes (MenSC-Ex) on AML12 cells (in vitro) and D-GalN/LPS-induced FHF mice (in vivo).

Methods

Transmission electron microscopy and Western blot were used to identify MenSC-Ex. Antibody array was used to examine cytokine levels on MenSC-Ex. MenSC-Ex were treated in D-GalN/LPS-induced AML12 in vitro. Cell proliferation and apoptosis were measured. MenSC-Ex were injected into the tail veins of mice 24 h before treatment with D-GalN/LPS. Blood and liver tissues served as physiological and biochemical indexes. The number of liver mononuclear cells (MNCs) and the amount of the active apoptotic protein caspase-3 were determined to elaborate the mechanism of hepatoprotective activity.

Results

Human menstrual blood-derived stem cell-derived exosomes (MenSC-Ex) are bi-lipid membrane vesicles that have a round, ball-like shape with a diameter of approximately 30–100 nm. Cytokine arrays have shown that MenSC-Ex expressed cytokines, including ICAM-1, angiopoietin-2, Axl, angiogenin, IGFBP-6, osteoprotegerin, IL-6, and IL-8. MenSC-Ex markedly improved liver function, enhanced survival rates, and inhibited liver cell apoptosis at 6 h after transplantation. MenSC-Ex migrated to sites of injury and to AML12 cells (a mouse hepatocyte cell line), respectively. Moreover, MenSC-Ex reduced the number of liver mononuclear cells (MNCs) and the amount of the active apoptotic protein caspase-3 in injured livers.

Conclusions

In conclusion, our results provide preliminary evidence for the anti-apoptotic capacity of MenSC-Ex in FHF and suggest that MenSC-Ex may be an alternative therapeutic approach to treat FHF.

Electronic supplementary material

The online version of this article (doi:10.1186/s13287-016-0453-6) contains supplementary material, which is available to authorized users.

The Role of Chemokines in Fibrotic Wound Healing

Significance: Main dermal forms of fibroproliferative disorders are hypertrophic scars (HTS) and keloids. They often occur after cutaneous wound healing after skin injury, or keloids even form spontaneously in the absence of any known injury. HTS and keloids are different in clinical performance, morphology, and histology, but they all lead to physical and psychological problems for survivors. Recent Advances: Although the mechanism of wound healing at cellular and tissue levels has been well described, the molecular pathways involved in wound healing, especially fibrotic healing, is incompletely understood. Critical Issues: Abnormal scars not only lead to increased health-care costs but also cause significant psychological problems for survivors. A plethora of therapeutic strategies have been used to prevent or attenuate excessive scar formation; however, most therapeutic approaches remain clinically unsatisfactory. Future Directions: Effective care depends on an improved understanding of the mechanisms that cause abnormal scars in patients. A thorough understanding of the roles of chemokines in cutaneous wound healing and abnormal scar formation will help provide more effective preventive and therapeutic strategies for dermal fibrosis as well as for other proliferative disorders.

Serum amyloid A1α induces paracrine IL-8/CXCL8 via TLR2 and directly synergizes with this chemokine via CXCR2 and formyl peptide receptor 2 to recruit neutrophils

Cell migration depends on the ability of leukocytes to sense an external gradient of chemotactic proteins produced during inflammation. These proteins include chemokines, complement factors, and some acute phase proteins, such as serum amyloid A. Serum amyloid A chemoattracts neutrophils, monocytes, and T lymphocytes via its G protein-coupled receptor formyl peptide receptor 2. We demonstrate that serum amyloid A1α more potently chemoattracts neutrophils in vivo than in vitro. In contrast to CD14(+) monocytes, no rapid (within 2 h) induction of interleukin-8/CXC chemokine ligand 8 or macrophage-inflammatory protein-1α/CC chemokine ligand 3 was observed in purified human neutrophils after stimulation of the cells with serum amyloid A1α or lipopolysaccharide. Moreover, interleukin-8/CXC chemokine ligand 8 induction in monocytes by serum amyloid A1α was mediated by toll-like receptor 2 and was inhibited by association of serum amyloid A1α with high density lipoprotein. This indicates that the potent chemotactic response of neutrophils toward intraperitoneally injected serum amyloid A1α is indirectly enhanced by rapid induction of chemokines in peritoneal cells, synergizing in a paracrine manner with serum amyloid A1α. We observed direct synergy between IL-8/CXC chemokine ligand 8 and serum amyloid A1α, but not lipopolysaccharide, in chemotaxis and shape change assays with neutrophils. Furthermore, the selective CXC chemokine receptor 2 and formyl peptide receptor 2 antagonists, SB225002 and WRW4, respectively, blocked the synergy between IL-8/CXC chemokine ligand 8 and serum amyloid A1α in neutrophil chemotaxis in vitro, indicating that for synergy their corresponding G protein-coupled receptors are required. Additionally, SB225002 significantly inhibited serum amyloid A1α-mediated peritoneal neutrophil influx. Taken together, endogenous (e.g., IL-1β) and exogenous (e.g., lipopolysaccharide) inflammatory mediators induce primary chemoattractants such as serum amyloid A that synergize in an autocrine (monocyte) or a paracrine (neutrophil) fashion with secondary chemokines induced in stromal cells.

Chemokine-guided cell migration and motility in zebrafish development

Chemokines are vertebrate-specific, structurally related proteins that function primarily in controlling cell movements by activating specific 7-transmembrane receptors. Chemokines play critical roles in a large number of biological processes and are also involved in a range of pathological conditions. For these reasons, chemokines are at the focus of studies in developmental biology and of clinically oriented research aimed at controlling cancer, inflammation, and immunological diseases. The small size of the zebrafish embryos, their rapid external development, and optical properties as well as the large number of eggs and the fast expansion in genetic tools available make this model an extremely useful one for studying the function of chemokines and chemokine receptors in an in vivo setting. Here, we review the findings relevant to the role that chemokines play in the context of directed single-cell migration, primarily in neutrophils and germ cells, and compare it to the collective cell migration of the zebrafish lateral line. We present the current knowledge concerning the formation of the chemokine gradient, its interpretation within the cell, and the molecular mechanisms underlying the cellular response to chemokine signals during directed migration.

Role of serine proteases in the regulation of interleukin-877 during the development of bronchopulmonary dysplasia in preterm ventilated infants

RATIONALE

The chemokine interleukin-8 is implicated in the development of bronchopulmonary dysplasia in preterm infants. The 77-amino acid isoform of interleukin-8 (interleukin-877) is a less potent chemoattractant than other shorter isoforms. Although interleukin-877 is abundant in the preterm circulation, its regulation in the preterm lung is unknown.

OBJECTIVES

To study expression and processing of pulmonary interleukin-877 in preterm infants who did and did not develop bronchopulmonary dysplasia.

METHODS

Total interleukin-8 and interleukin-877 were measured in bronchoalveolar lavage fluid from preterm infants by immunoassay. Neutrophil serine proteases were used to assess processing. Neutrophil chemotaxis assays and degranulation of neutrophil matrix metalloproteinase-9 were used to assess interleukin-8 function.

MAIN RESULTS

Peak total interleukin-8 and interleukin-877 concentrations were increased in infants who developed bronchopulmonary dysplasia compared to those who did not. Shorter forms of interleukin-8 predominated in the preterm lung (96.3% No-bronchopulmonary dysplasia vs 97.1% bronchopulmonary dysplasia, p>0.05). Preterm bronchoalveolar lavage fluid significantly converted exogenously added interleukin-877 to shorter isoforms (p<0.001). Conversion was greater in bronchopulmonary dysplasia infants (p<0.05). This conversion was inhibited by α-1 antitrypsin and antithrombin III (p<0.01). Purified neutrophil serine proteases efficiently converted interleukin-877 to shorter isoforms in a time- and dose-dependent fashion; shorter interleukin-8 isoforms were primarily responsible for neutrophil chemotaxis (p<0.001). Conversion by proteinase-3 resulted in significantly increased interleukin-8 activity in vitro (p<0.01).

CONCLUSIONS

Shorter, potent, isoforms interleukin-8 predominate in the preterm lung, and are increased in infants developing bronchopulmonary dysplasia, due to conversion of interleukin-877 by neutrophil serine proteases and thrombin. Processing of interleukin-8 provides an attractive therapeutic target to prevent development of bronchopulmonary dysplasia.

Serum amyloid A chemoattracts immature dendritic cells and indirectly provokes monocyte chemotaxis by induction of cooperating CC and CXC chemokines

Serum amyloid A (SAA) is an acute phase protein that is upregulated in inflammatory diseases and chemoattracts monocytes, lymphocytes, and granulocytes via its G protein-coupled receptor formyl peptide receptor like 1/formyl peptide receptor 2 (FPRL1/FPR2). Here, we demonstrated that the SAA1α isoform also chemoattracts monocyte-derived immature dendritic cells (DCs) in the Boyden and μ-slide chemotaxis assay and that its chemotactic activity for monocytes and DCs was indirectly mediated via rapid chemokine induction. Indeed, SAA1 induced significant amounts (≥5 ng/mL) of macrophage inflammatory protein-1α/CC chemokine ligand 3 (MIP-1α/CCL3) and interleukin-8/CXC chemokine ligand 8 (IL-8/CXCL8) in monocytes and DCs in a dose-dependent manner within 3 h. However, SAA1 also directly activated monocytes and DCs for signaling and chemotaxis without chemokine interference. SAA1-induced monocyte migration was nevertheless significantly prevented (60-80% inhibition) in the constant presence of desensitizing exogenous MIP-1α/CCL3, neutralizing anti-MIP-1α/CCL3 antibody, or a combination of CC chemokine receptor 1 (CCR1) and CCR5 antagonists, indicating that this endogenously produced CC chemokine was indirectly contributing to SAA1-mediated chemotaxis. Further, anti-IL-8/CXCL8 antibody neutralized SAA1-induced monocyte migration, suggesting that endogenous IL-8/CXCL8 acted in concert with MIP-1α/CCL3. This explained why SAA1 failed to synergize with exogenously added MIP-1α/CCL3 or stromal cell-derived factor-1α (SDF-1α)/CXCL12 in monocyte and DC chemotaxis. In addition to direct leukocyte activation, SAA1 induces a chemotactic cascade mediated by expression of cooperating chemokines to prolong leukocyte recruitment to the inflammatory site.

On the structure and functions of gelatinase B/matrix metalloproteinase-9 in neuroinflammation

The blood-brain barrier (BBB) is a specific structure that is composed of two basement membranes (BMs) and that contributes to the control of neuroinflammation. As long as the BBB is intact, extravasated leukocytes may accumulate between two BMs, generating vascular cuffs. Specific matrix metalloproteinases, MMP-2 and MMP-9, have been shown to cleave BBB beta-dystroglycan and to disintegrate thereby the parenchymal BM, resulting in encephalomyelitis. This knowledge has been added to the molecular basis of the REGA model to understand the pathogenesis of multiple sclerosis, and it gives further ground for the use of MMP inhibitors for the treatment of acute neuroinflammation. MMP-9 is associated with central nervous system inflammation and occurs in various forms: monomers and multimers. None of the various neurological and neuropathologic functions of MMP-9 have been associated with either molecular structure or molecular form, and therefore, in-depth structure-function studies are needed before medical intervention with MMP-9-specific inhibitors is initiated.

In vivo regulation of chemokine activity by post-translational modification

Cytokines and chemokines represent two important groups of proteins that control the immune system. Dysregulation of the network in which these immunomodulators function can result in uncontrolled inflammation leading to various diseases, including rheumatoid arthritis, characterized by chronic inflammation and bone erosion. Chemokine activity is regulated at multiple levels, such as post-translational modification (PTM) of chemokines and their receptors by specific enzymes including proteases and peptidylarginine deiminases. Many in vitro experiments underscore the importance of post-translational processing of human chemokines. PTMs may enhance or reduce chemokine activity or may alter the receptor specificity of chemokine ligands. However, identification of chemokine isoforms in physiological in vivo settings forms the ultimate proof that PTM of chemokines is relevant in regulating the biological activity of these molecules. This review summarizes current knowledge on the in vivo role for PTMs in the regulation of chemokine activity.

Chemokines shape the immune responses to tuberculosis

Mycobacterium tuberculosis (Mtb) is the intracellular pathogen that causes the disease, tuberculosis. Chemokines and chemokine receptors are key regulators in immune cell recruitment to sites of infection and inflammation. This review highlights our recent advances in understanding the role of chemokines and chemokine receptors in cellular recruitment of immune cells to the lung, role in granuloma formation and host defense against Mtb infection.

The role of CXC chemokines in the transition of chronic inflammation to esophageal and gastric cancer

Chronic inflammation may increase the risk to develop cancer, for instance esophagitis or gastritis may lead to development of esophageal or gastric cancer, respectively. The key molecules attracting leukocytes to local inflammatory sites are chemokines. We here provide a systematic review on the impact of CXC chemokines (binding the receptors CXCR1, CXCR2, CXCR3 and CXCR4) on the transition of chronic inflammation in the upper gastrointestinal tract to neoplasia. CXCR2 ligands, including GRO-α,β,γ/CXCL1,2,3, ENA-78/CXCL5 and IL-8/CXCL8 chemoattract pro-tumoral neutrophils. In addition, angiogenic CXCR2 ligands stimulate the formation of new blood vessels, facilitating tumor progression. The CXCR4 ligand SDF-1/CXCL12 also promotes tumor development by stimulating angiogenesis and by favoring metastasis of CXCR4-positive tumor cells to distant organs producing SDF-1/CXCL12. Furthermore, these angiogenic chemokines also directly enhance tumor cell survival and proliferation. In contrast, the CXCR3 ligands Mig/CXCL9, IP-10/CXCL10 and I-TAC/CXCL11 are angiostatic and attract anti-tumoral T lymphocytes and may therefore mediate tumor growth retardation and regression. Thus, chemokines exert diverging, sometimes dual roles in tumor biology as described for esophageal and gastric cancer. Therefore extensive research is needed to completely unravel the complex chemokine code in specific cancers. Possibly, chemokine-targeted cancer therapy will have to be adapted to the individual's chemokine profile.

The expression and role of CXC chemokines in colorectal cancer

Cancer is a life-threatening disease world-wide and colorectal cancer is the second common cause of cancer mortality. The interaction between tumor cells and stromal cells plays a crucial role in tumor initiation and progression and is partially mediated by chemokines. Chemokines predominantly participate in the chemoattraction of leukocytes to inflammatory sites. Nowadays, it is clear that CXC chemokines and their receptors (CXCR) may also modulate tumor behavior by several important mechanisms: regulation of angiogenesis, activation of a tumor-specific immune response by attracting leukocytes, stimulation of tumor cell proliferation and metastasis. Here, we review the expression and complex roles of CXC chemokines (CXCL1 to CXCL16) and their receptors (CXCR1 to CXCR6) in colorectal cancer. Overall, increased expression levels of CXC chemokines correlate with poor prognosis.

A self-propagating matrix metalloprotease-9 (MMP-9) dependent cycle of chronic neutrophilic inflammation

Background

Chronic neutrophilic inflammation is a poorly understood feature in a variety of diseases with notable worldwide morbidity and mortality. We have recently characterized N-acetyl Pro-Gly-Pro (Ac-PGP) as an important neutrophil (PMN) chemoattractant in chronic inflammation generated from the breakdown of collagen by the actions of MMP-9. MMP-9 is present in the granules of PMNs and is differentially released during inflammation but whether Ac-PGP contributes to this ongoing proteolytic activity in chronic neutrophilic inflammation is currently unknown.

Methodology/Principal Findings

Utilizing isolated primary blood PMNs from human donors, we found that Ac-PGP induces significant release of MMP-9 and concurrently activates the ERK1/2 MAPK pathway. This MMP-9 release is attenuated by an inhibitor of ERK1/2 MAPK and upstream blockade of CXCR1 and CXCR2 receptors with repertaxin leads to decreased MMP-9 release and ERK 1/2 MAPK activation. Supernatants obtained from PMNs stimulated by Ac-PGP generate more Ac-PGP when incubated with intact collagen ex vivo; this effect is inhibited by an ERK1/2 pathway inhibitor. Finally, clinical samples from individuals with CF demonstrate a notable correlation between Ac-PGP (as measured by liquid chromatography-tandem mass spectrometry) and MMP-9 levels even when accounting for total PMN burden.

Conclusions/Significance

These data indicate that ECM-derived Ac-PGP could result in a feed-forward cycle by releasing MMP-9 from activated PMNs through the ligation of CXCR1 and CXCR2 and subsequent activation of the ERK1/2 MAPK, highlighting for the first time a matrix-derived chemokine (matrikine) augmenting its generation through a discrete receptor/intracellular signaling pathway. These findings have notable implications to the development unrelenting chronic PMN inflammation in human disease.