Murine CXCR1 is a functional receptor for GCP-2/CXCL6 and interleukin-8/CXCL8

Directing B7-H3 chimeric antigen receptor T cell homing through IL-8 induces potent antitumor activity against pediatric sarcoma

BACKGROUND

Advances in pediatric oncology have occurred for some cancers; however, new therapies for sarcoma have been inadequate. Cellular immunotherapy using chimeric antigen receptor (CAR) T cells has shown dramatic benefits in leukemia, lymphoma, and multiple myeloma but has been far less successful in pediatric solid tumors such as rhabdomyosarcoma (RMS) and osteosarcoma (OS). Balancing issues of "on-target, off-tumor toxicity", investigators have identified B7-H3 as a broadly expressed tumor antigen with otherwise restricted expression on normal tissues. We hypothesized that rapid homing via a chemokine receptor and CAR engagement through B7-H3 would enhance CAR T cell efficacy in solid tumors.

METHODS

We generated B7-H3 CAR T cells that also express the Interleukin-8 (IL-8) receptor, CXCR2. Cytokine production, flow cytometry, Seahorse assays and RNA sequencing were used to compare the B7-H3 CXCR2 (BC2) CAR T cells with B7-H3 CAR T cells. We developed an IL-8 overexpressing human RMS mouse model to test homing and cytotoxicity in vivo.

RESULTS

We demonstrate that IL-8 is expressed by RMS and OS and expression significantly increases after radiation. Overexpression of an IL-8 receptor, CXCR2, on B7-H3 CAR T cells enhances homing into IL-8 expressing tumors, augments T cell metabolism and leads to significant tumor regression.

CONCLUSION

These findings warrant further investigation into the use of BC2 CAR T cells as a treatment for patients with RMS, OS and other B7-H3-expressing, IL-8 producing solid tumors.

Single-cell analysis identifies PLK1 as a driver of immunosuppressive tumor microenvironment in LUAD

PLK1 (Polo-like kinase 1) plays a critical role in the progression of lung adenocarcinoma (LUAD). Recent studies have unveiled that targeting PLK1 improves the efficacy of immunotherapy, highlighting its important role in the regulation of tumor immunity. Nevertheless, our understanding of the intricate interplay between PLK1 and the tumor microenvironment (TME) remains incomplete. Here, using genetically engineered mouse model and single-cell RNA-seq analysis, we report that PLK1 promotes an immunosuppressive TME in LUAD, characterized with enhanced M2 polarization of tumor associated macrophages (TAM) and dampened antigen presentation process. Mechanistically, elevated PLK1 coincides with increased secretion of CXCL2 cytokine, which promotes M2 polarization of TAM and diminishes expression of class II major histocompatibility complex (MHC-II) in professional antigen-presenting cells. Furthermore, PLK1 negatively regulates MHC-II expression in cancer cells, which has been shown to be associated with compromised tumor immunity and unfavorable patient outcomes. Taken together, our results reveal PLK1 as a novel modulator of TME in LUAD and provide possible therapeutic interventions.

Hybrid epithelial-mesenchymal status of lung cancer dictates metastatic success through differential interaction with NK cells

BACKGROUND

Epithelial to mesenchymal transition (EMT) endows cancer cells with pro-metastatic properties, which appear most effective when cells enter an intermediate hybrid (H) state, characterized by integrated mesenchymal (M) and epithelial (E) traits. The reasons for this advantage are poorly known and, especially, it is totally unexplored whether the interplay between H-cells and NK cells could have a role. Here we characterize the pro-metastatic mechanics of non-small cell lung cancer (NSCLC) H-cells and their subset of cancer-initiating cells (CICs), dissecting crucial interactions with NK cells.

METHODS

Human lung cancer cell lines and sublines representative of E, M, or H states, assessed by proteomics, were analyzed in vivo for their tumor-forming and disseminating capabilities. Interactions with NK cells were investigated in vitro using migration assays, cytotoxic degranulation assays, and evaluation of CD133+ CICs modulation after coculture, and validated in vivo through NK cell neutralization assays. Correlation between EMT status, NK cell infiltration, and survival data, was evaluated in a cohort of surgically resected NSCLC cases (n=79).

RESULTS

We demonstrated that H-cells, have limited dissemination capability but show the highest potential to initiate metastases in vivo. This property was related to their ability to escape NK cell surveillance. Mechanistically, H-cells expressed low levels of NK-attracting chemokines (CXCL1 and CXCL8), generating poorly infiltrated metastases. Accordingly, proteomics and GO enrichment analysis of E, H, M cell lines showed that the related secretory processes could change during EMT.Furthermore, H-CICs uniquely expressed high levels of the inhibitory ligand B7-H3, which protected H-CIC from NK cell-mediated clearance. In vivo neutralization assays confirmed that, indeed, the pro-metastatic properties of H-cells are poorly controlled by NK cells.Finally, the analysis of patients revealed that detection of hybrid phenotypes associated with low NK infiltration in NSCLC clinical specimens could identify a subset of patients with poor prognosis.

CONCLUSIONS

Our study demonstrates that H-cells play a central role in the metastatic spread in NSCLC. Such pro-metastatic advantage of H-cells is supported by their altered interaction with NK cells and by the critical role of B7-H3 in preserving their H-CIC component, indicating B7-H3 as a potential target in combined NK-based therapies.

Neutrophil extracellular traps induced by chemotherapy inhibit tumor growth in murine models of colorectal cancer

Neutrophil extracellular traps (NETs), a web-like structure of cytosolic and granule proteins assembled on decondensed chromatin, kill pathogens and cause tissue damage in diseases. Whether NETs can kill cancer cells is unexplored. Here, we report that a combination of glutaminase inhibitor CB-839 and 5-FU inhibited the growth of PIK3CA-mutant colorectal cancers (CRCs) in xenograft, syngeneic, and genetically engineered mouse models in part through NETs. Disruption of NETs by either DNase I treatment or depletion of neutrophils in CRCs attenuated the efficacy of the drug combination. Moreover, NETs were present in tumor biopsies from patients treated with the drug combination in a phase II clinical trial. Increased NET levels in tumors were associated with longer progression-free survival. Mechanistically, the drug combination induced the expression of IL-8 preferentially in PIK3CA-mutant CRCs to attract neutrophils into the tumors. Further, the drug combination increased the levels of ROS in neutrophils, thereby inducing NETs. Cathepsin G (CTSG), a serine protease localized in NETs, entered CRC cells through the RAGE cell surface protein. The internalized CTSG cleaved 14-3-3 proteins, released BAX, and triggered apoptosis in CRC cells. Thus, our studies illuminate a previously unrecognized mechanism by which chemotherapy-induced NETs kill cancer cells.

Natural Products as Dietary Agents for the Prevention and Mitigation of Oxidative Damage and Inflammation in the Intestinal Barrier

Food intake is a basic need to sustain life, but foodborne pathogens and food-related xenobiotics are also the main health concerns regarding intestinal barrier homeostasis. With a predominant role in the well-being of the entire human body, intestinal barrier homeostasis is strictly regulated by epithelial and immune cells. These cells are also the main intervenients in oxidative stress and inflammation-related diseases in the intestinal tract, triggered, for example, by genetic/epigenetic factors, food additives, pesticides, drugs, pathogens, and their metabolites. Nevertheless, the human diet can also be seen as a solution for the problem, mainly via the inclusion of functional foods or nutraceuticals that may act as antioxidant/anti-inflammatory agents to prevent and mitigate acute and chronic oxidative damage and inflammation. A literature analysis of recent advances in this topic highlights the significant role of Nrf2 (nuclear factor erythroid 2-related factor 2) and NF-kB (nuclear factor kappa-light-chain-enhancer of activated B cells) pathways in these biological processes, with many natural products and phytochemicals targeting endogenous antioxidant systems and cytokine production and balance. In this review, we summarized and discussed studies using in vitro and in vivo models of the intestinal tract used to reproduce oxidative damage and inflammatory events, as well as the role of natural products as modulators of Nrf2 and NK-kB pathways.

LMP1 and EBNA2 constitute a minimal set of EBV genes for transformation of human B cells

Introduction

Epstein-Barr virus (EBV) infection in humans is associated with a wide range of diseases including malignancies of different origins, most prominently B cells. Several EBV latent genes are thought to act together in B cell immortalization, but a minimal set of EBV genes sufficient for transformation remains to be identified.

Methods

Here, we addressed this question by transducing human peripheral B cells from EBV-negative donors with retrovirus expressing the latent EBV genes encoding Latent Membrane Protein (LMP) 1 and 2A and Epstein-Barr Nuclear Antigen (EBNA) 2.

Results

LMP1 together with EBNA2, but not LMP1 alone or in combination with LMP2A was able to transform human primary B cells. LMP1/EBNA2-immortalized cell lines shared surface markers with EBV-transformed lymphoblastoid cell lines (LCLs). They showed sustained growth for more than 60 days, albeit at a lower growth rate than EBV-transformed LCLs. LMP1/EBNA2-immortalized cell lines generated tumors when transplanted subcutaneously into severely immunodeficient NOG mice.

Conclusion

Our results identify a minimal set of EBV proteins sufficient for B cell transformation.

Targeting cancer-associated adipocyte-derived CXCL8 inhibits triple-negative breast cancer progression and enhances the efficacy of anti-PD-1 immunotherapy

Cancer-associated adipocytes (CAAs), one of the primary stromal components, exhibit intimate crosstalk and release multiple cell factors mediating local and systemic biological effects. However, the role of CAAs in the regulation of systemic immune responses and their potential value in the clinical treatment of triple-negative breast cancer (TNBC) are not well described. Transcriptome sequencing was performed on CAA and normal adipocyte (NA) tissues isolated from surgically resected samples from TNBC patients and healthy controls. Cytokines, including C-X-C motif chemokine ligand 8 (CXCL8, also known as IL-8), secreted from NAs and CAAs were compared by transcriptome sequencing and enzyme-linked immunosorbent assay (ELISA). Proliferation, migration and invasion assays were employed to analyze the role of CAAs and CAA-derived CXCL8 (macrophage inflammatory protein-2 (MIP2) as a functional surrogate in mice). TNBC syngraft models were established to evaluate the curative effect of targeting CXCL8 in combination with anti-PD-1 therapies. Real-time quantitative polymerase chain reaction (RT-qPCR), western blotting (WB), polymerase chain reaction (PCR) array, flow cytometry, immunohistochemistry (IHC), and immunofluorescence (IF) were applied to analyze immune cell infiltration and epithelial-mesenchymal transition (EMT) markers. Specifically, we demonstrated that CAAs and CAA-derived CXCL8 played important roles in tumor growth, EMT, metastasis and tumor immunity suppression. CAA-derived CXCL8 remodeled the tumor immune microenvironment not only by suppressing CD4+ T and CD8+ T immune cell infiltration but also by upregulating CD274 expression in TNBC. The combination of targeting the CXCL8 pathway and blocking the PD-1 pathway synergistically increased the tumor immune response and inhibited tumor progression. Thus, our results highlight the molecular mechanisms and translational significance of CAAs in tumor progression and immune ecosystem regulatory effects and provide a better understanding of the potential clinical benefit of targeting CAA-derived CXCL8 in antitumor immunity and as a new therapeutic moiety in TNBC.

Chemokines, molecular drivers of thromboinflammation and immunothrombosis

Blood clotting is a finely regulated process that is essential for hemostasis. However, when dysregulated or spontaneous, it promotes thrombotic disorders. The fact that these are triggered, accompanied and amplified by inflammation is reflected in the term thromboinflammation that includes chemokines. The role of chemokines in thrombosis is therefore illuminated from a cellular perspective, where endothelial cells, platelets, red blood cells, and leukocytes may be both the source and target of chemokines. Chemokine-dependent prothrombotic processes may thereby occur independently of chemokine receptors or be mediated by chemokine receptors, although the binding and activation of classical G protein-coupled receptors and their signaling pathways differ from those of atypical chemokine receptors, which do not function via cell activation and recruitment. Regardless of binding to their receptors, chemokines can induce thrombosis by forming platelet-activating immune complexes with heparin or other polyanions that are pathognomonic for HIT and VITT. In addition, chemokines can bind to NETs and alter their structure. They also change the electrical charge of the cell surface of platelets and interact with coagulation factors, thereby modulating the balance of fibrinolysis and coagulation. Moreover, CXCL12 activates CXCR4 on platelets independently of classical migratory chemokine activity and causes aggregation and thrombosis via the PI3Kβ and Btk signaling pathways. In contrast, typical chemokine-chemokine receptor interactions are involved in the processes that contribute to the adhesiveness of the endothelium in the initial phase of venous thrombosis, where neutrophils and monocytes subsequently accumulate in massive numbers. Later, the reorganization and resolution of a thrombus require coordinated cell migration and invasion of the thrombus, and, as such, indeed, chemokines recruit leukocytes to existing thrombi. Therefore, chemokines contribute in many independent ways to thrombosis.

Human CXCR1 knock-in mice infer functional expression of a murine ortholog

Targeting CXCR1 and CXCR2 chemokine receptors to block neutrophil migration to sites of inflammation is a promising therapeutic approach for various inflammatory and autoimmune diseases. However, assessing the translational potential of such therapies using mouse models is challenging due to the unclear expression of CXCR1 at the protein level. Although CXCR2 has been well characterized in both mice and humans, the protein-level expression of CXCR1 in mice (mCXCR1) remains controversial. To address this issue, we generated a novel human CXCR1 knock-in (hCXCR1 KI) mouse model in which the transgene is under the control of the native mouse promoter and regulatory elements. Using an anti-human CXCR1 monoclonal antibody (anti-hCXCR1 monoclonal antibody), we found that hCXCR1 was highly expressed on neutrophils in the hCXCR1 KI mice, comparable to levels observed in human neutrophils. This successful expression of hCXCR1 in this mouse model suggests that functional mCXCR1 likely exists. To investigate the functional role of CXCR1, we investigated how antagonizing this receptor using anti-hCXCR1 monoclonal antibody in the arthritis model would affect disease outcomes. Antibody treatment significantly alleviated all signs of joint inflammation. In summary, our newly generated hCXCR1 KI transgenic mice provide a valuable tool to investigate the therapeutic efficacy of small molecules or monoclonal antibodies that antagonize this receptor in neutrophil-mediated pathologies.

Single-cell analysis characterizes PLK1 as a catalyst of an immunosuppressive tumor microenvironment in LUAD

PLK1 (Polo-like kinase 1) plays a critical role in the progression of lung adenocarcinoma (LUAD). Recent studies have unveiled that targeting PLK1 improves the efficacy of immunotherapy, highlighting its important role in the regulation of tumor immunity. Nevertheless, our understanding of the intricate interplay between PLK1 and the tumor microenvironment (TME) remains incomplete. Here, using genetically engineered mouse model and single-cell RNA-seq analysis, we report that PLK1 promotes an immunosuppressive TME in LUAD, characterized with enhanced M2 polarization of tumor associated macrophages (TAM) and dampened antigen presentation process. Mechanistically, elevated PLK1 coincides with increased secretion of CXCL2 cytokine, which promotes M2 polarization of TAM and diminishes expression of class II major histocompatibility complex (MHC-II) in professional antigen-presenting cells. Furthermore, PLK1 negatively regulates MHC-II expression in cancer cells, which has been shown to be associated with compromised tumor immunity and unfavorable patient outcomes. Taken together, our results reveal PLK1 as a novel modulator of TME in LUAD and provide possible therapeutic interventions.

Granulocyte development, tissue recruitment, and function during allergic inflammation

Granulocytes provide a fast innate response to pathogens and allergens. In allergy and anti-helminth immunity, epithelial cells of damaged barriers release alarmins like IL-25, IL-33, and thymic stromal lymphopoietin (TSLP) but also chemokines like CXCL1 or CCL11 to promote cell recruitment and inflammation. In addition, mast cells positioned at barrier tissue sites also quickly release mediators upon specifically sensing antigens through IgE bound to FcεR1 on their surface. Released mediators induce the recruitment of different granulocytes in a timely ordered manner. First, neutrophils extravasate from the blood vasculature to the side of alarmin release and promote a potent inflammatory response. Alarmins and activated mast cells further promote activation of ILC2s and recruitment of basophils and eosinophils, which inhibit neutrophil recruitment and enhance tissue type 2 immunity. In addition to their potent pro-inflammatory effector functions, granulocytes can also contribute to termination and resolution of inflammation. Here, we summarize the development and tissue recruitment of granulocyte subsets, and describe general effector functions and aspects of their increasingly appreciated role in limiting tissue damage. We further discuss targeting approaches for therapeutic interventions in allergic disorders.

CXCR2 expression during melanoma tumorigenesis controls transcriptional programs that facilitate tumor growth

BACKGROUND

Though the CXCR2 chemokine receptor is known to play a key role in cancer growth and response to therapy, a direct link between expression of CXCR2 in tumor progenitor cells during induction of tumorigenesis has not been established.

METHODS

To characterize the role of CXCR2 during melanoma tumorigenesis, we generated tamoxifen-inducible tyrosinase-promoter driven BrafV600E/Pten-/-/Cxcr2-/- and NRasQ61R/INK4a-/-/Cxcr2-/- melanoma models. In addition, the effects of a CXCR1/CXCR2 antagonist, SX-682, on melanoma tumorigenesis were evaluated in BrafV600E/Pten-/- and NRasQ61R/INK4a-/- mice and in melanoma cell lines. Potential mechanisms by which Cxcr2 affects melanoma tumorigenesis in these murine models were explored using RNAseq, mMCP-counter, ChIPseq, and qRT-PCR; flow cytometry, and reverse phosphoprotein analysis (RPPA).

RESULTS

Genetic loss of Cxcr2 or pharmacological inhibition of CXCR1/CXCR2 during melanoma tumor induction resulted in key changes in gene expression that reduced tumor incidence/growth and increased anti-tumor immunity. Interestingly, after Cxcr2 ablation, Tfcp2l1, a key tumor suppressive transcription factor, was the only gene significantly induced with a log2 fold-change greater than 2 in these three different melanoma models.

CONCLUSIONS

Here, we provide novel mechanistic insight revealing how loss of Cxcr2 expression/activity in melanoma tumor progenitor cells results in reduced tumor burden and creation of an anti-tumor immune microenvironment. This mechanism entails an increase in expression of the tumor suppressive transcription factor, Tfcp2l1, along with alteration in the expression of genes involved in growth regulation, tumor suppression, stemness, differentiation, and immune modulation. These gene expression changes are coincident with reduction in the activation of key growth regulatory pathways, including AKT and mTOR.

Molecular characterization, structural and expression analysis of twelve CXC chemokines and eight CXC chemokine receptors in largemouth bass (Micropterus salmoides)

The chemokine-receptor system plays important roles in the leukocyte trafficking, inflammation, immune cell differentiation, cancer and other biological processes. In the present study, the sequence features, structures and expression patterns of twelve CXC chemokine ligands (CXCL8a.1, CXCL8a.2, CXCL8b.1, CXCL8b.2, CXCL12a, CXCL12b, CXCL13.1, CXCL13.2, CXCL14, CXCL18a, CXCL18b and CXCL19) and eight CXC chemokine receptors (CXCR1, CXCR2, CXCR3.1, CXCR3.2, CXCR3.3, CXCR4a, CXCR4b and CXCR5) of largemouth bass (Micropterus salmoides) were analyzed. All the CXCLs and CXCRs of largemouth bass shared high sequence identities with their teleost counterparts and possessed conserved motifs and structures of CXCLs and CXCRs family. Realtime qPCR revealed that these CXCLs and CXCRs were ubiquitously expressed in all examined tissues, with high expression levels in the immune-related tissues (spleen, head kidney, and gill). Following lipopolysaccharide (LPS) and polyinosinic-polycytidylic acid (polyI:C) stimulations, most of these CXCLs and CXCRs were significantly up-regulated in spleen. In addition, the potential interacted molecules of these CXCLs and CXCRs were analyzed by protein-protein interaction network analysis. To the best of our knowledge, this is the first study that in detail analyzes the CXCLs and CXCRs of largemouth bass. Our results provide valuable basis for study the function and mechanism of chemokine-receptor system in largemouth bass.

Constraint-induced movement therapy alleviates motor impairment by inhibiting the accumulation of neutrophil extracellular traps in ischemic cortex

Stroke is a major cause of mortality and morbidity and most acute strokes are ischemic. Evidence-based medicine has demonstrated the effectiveness of constraint-induced movement therapy (CIMT) in the recovery of motor function in patients after ischemic stroke, but the specific treatment mechanism remains unclear. Herein, our integrated transcriptomics and multiple enrichment analysis studies, including Gene Ontology (GO), Kyoto Encyclopedia of Genes and Genomes (KEGG), and gene set enrichment analysis (GSEA) studies show that CIMT conduction broadly curtails immune response, neutrophil chemotaxis, and chemokine-mediated signaling pathway, CCR chemokine receptor binding. Those suggest the potential effect of CIMT on neutrophils in ischemic mice brain parenchyma. Recent studies have found that accumulating granulocytes release extracellular web-like structures composed of DNA and proteins called neutrophil extracellular traps (NETs), which destruct neurological function primarily by disrupting the blood-brain barrier and promoting thrombosis. However, the temporal and spatial distribution of neutrophils and their released NETs in parenchyma and their damaging effects on nerve cells remain unclear. Thus, utilizing immunofluorescence and flow cytometry, our analyses uncovered that NETs erode multiple regions such as primary motor cortex (M1), striatum (Str), nucleus of the vertical limb of the diagonal band (VDB), nucleus of the horizontal limb of the diagonal band (HDB) and medial septal nucleus (MS), and persist in the brain parenchyma for at least 14 days, while CIMT can reduce the content of NETs and chemokines CCL2 and CCL5 in M1. Intriguingly, CIMT failed to further reduce neurological deficits after inhibiting the NET formation by pharmacologic inhibition of peptidylarginine deiminase 4 (PAD4). Collectively, these results demonstrate that CIMT could alleviate cerebral ischemic injury induced locomotor deficits by modulating the activation of neutrophils. These data are expected to provide direct evidence for the expression of NETs in ischemic brain parenchyma and novel insights into the mechanisms of CIMT protecting against ischemic brain injury.

Tumor cell density dependent IL-8 secretion induces the fluctuation of tregs/CD8 + T cells infiltration in hepatocellular carcinoma: one prompt for the existence of density checkpoint

BACKGROUND

Tumor cell density is a basic pathological feature of solid tumors. Chemotherapy, radiotherapy, and targeted therapy reduce tumor cell density, whereas unrestricted tumor cell proliferation promotes this feature. The impact of tumor cells on the microenvironment following changes in tumor cell density is still unclear. In this study, we focused on the response of key immune cell subsets to tumor cell density in hepatocellular carcinoma (HCC).

METHODS

We determined the density of tumor and immune cells in the same area by section staining. We then identified potential mediators using polymerase chain reaction (PCR), enzyme-linked immunofluorescence assay (ELISA), 3D and co-culture, flow cytometry, and lentivirus intervention. The mechanism of lactate promotion was verified using lactate tests, bioinformatics, western blotting, and the above methods. The IL-8/DAPK1/lactate/regulatory T cell (Treg) axis was verified using a mouse liver cancer model. Tumor mutation burden was calculated using maftools in R.

RESULTS

We found that the Treg/CD8 + T cell ratio is not consistent with tumor cell density in HCC, and a decreased Treg/CD8 + T cell ratio in the range of 5000-6000 cells/mm² may elicit the possibility for immunotherapy in an immunosuppressive microenvironment. We showed that IL-8 mediates this immune fluctuation and promotes the infiltration of Tregs through the DAPK1/pyruvate kinase activity/lactate axis in HCC. Based on tumor ploidy and mutation burden data, we discussed the potential significance of immune fluctuation in the homeostasis of HCC mutation burden and proposed a "density checkpoint" and "entropy model" to describe this phenomenon.

CONCLUSIONS

In summary, we report the mode of infiltration of Tregs/CD8 + T cells in response to tumor cell density and provide a new theoretical basis for IL-8 as a therapeutic target and the selection of an immunotherapy window in HCC.

Mechanisms of drug resistance in breast cancer liver metastases: Dilemmas and opportunities

Breast cancer is the leading cause of cancer-related deaths in females worldwide, and the liver is one of the most common sites of distant metastases in breast cancer patients. Patients with breast cancer liver metastases face limited treatment options, and drug resistance is highly prevalent, leading to a poor prognosis and a short survival. Liver metastases respond extremely poorly to immunotherapy and have shown resistance to treatments such as chemotherapy and targeted therapies. Therefore, to develop and to optimize treatment strategies as well as to explore potential therapeutic approaches, it is crucial to understand the mechanisms of drug resistance in breast cancer liver metastases patients. In this review, we summarize recent advances in the research of drug resistance mechanisms in breast cancer liver metastases and discuss their therapeutic potential for improving patient prognoses and outcomes.

CXCR2 expression during melanoma tumorigenesis controls transcriptional programs that facilitate tumor growth

Background

Though the CXCR2 chemokine receptor is known to play a key role in cancer growth and response to therapy, a direct link between expression of CXCR2 in tumor progenitor cells during induction of tumorigenesis has not been established.

Methods

To characterize the role of CXCR2 during melanoma tumorigenesis, we generated tamoxifen-inducible tyrosinase-promoter driven Braf ^V600E /Pten ^-/- /Cxcr2 ^-/- and NRas ^Q61R /INK4a ^-/- /Cxcr2 ^-/- melanoma models. In addition, the effects of a CXCR1/CXCR2 antagonist, SX-682, on melanoma tumorigenesis were evaluated in Braf ^V600E /Pten ^-/- and NRas ^Q61R /INK4a ^-/- mice and in melanoma cell lines. Potential mechanisms by which Cxcr2 affects melanoma tumorigenesis in these murine models were explored using RNAseq, mMCP-counter, ChIPseq, and qRT-PCR; flow cytometry, and reverse phosphoprotein analysis (RPPA).

Results

Genetic loss of Cxcr2 or pharmacological inhibition of CXCR1/CXCR2 during melanoma tumor induction resulted in key changes in gene expression that reduced tumor incidence/growth and increased anti-tumor immunity. Interestingly, after Cxcr2 ablation, Tfcp2l1 , a key tumor suppressive transcription factor, was the only gene significantly induced with a log ₂ fold-change greater than 2 in these three different melanoma models.

Conclusions

Here, we provide novel mechanistic insight revealing how loss of Cxcr2 expression/activity in melanoma tumor progenitor cells results in reduced tumor burden and creation of an anti-tumor immune microenvironment. This mechanism entails an increase in expression of the tumor suppressive transcription factor, Tfcp2l1, along with alteration in the expression of genes involved in growth regulation, tumor suppression, stemness, differentiation, and immune modulation. These gene expression changes are coincident with reduction in the activation of key growth regulatory pathways, including AKT and mTOR.

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.

Studies with neutralizing antibodies suggest CXCL8-mediated neutrophil activation is independent of C-C motif chemokine receptor-like 2 (CCRL2) ligand binding function

C-C motif chemokine receptor-like 2 (CCRL2) is a non-signaling 7 transmembrane receptor that binds chemotactic ligands to shape leukocyte recruitment to sites of inflammation. However, there is a lack of consensus on the ligands that directly bind CCRL2 or their functional impact. Studies with CCRL2 knockout mice have demonstrated that neutrophils have impaired degranulation and migration in response to CXCL8, where the underlying molecular mechanism is proposed to be due to the formation of CCRL2 heterodimers with the chemokine receptor CXCR2. Herein, we characterized the ligands that bind directly to CCRL2 and interrogated the impact of CCRL2 neutralization on CXCL8 signaling in neutrophils using pharmacological antibody tools. Using flow cytometry and Surface Plasmon Resonance microscopy (SPRm) cell binding experiments, we confirmed that chemerin, but not previously reported C-C chemokines, binds CCRL2. Furthermore, we identified human and mouse CCRL2 antibodies that neutralized chemerin binding to CCRL2. Unexpectedly, we found that neutralization of CCRL2 with these antibodies did not attenuate CXCL8-induced human neutrophil degranulation nor CXCL8-induced murine neutrophil recruitment to the peritoneum. Based on the observed differences in modulating CCRL2 function with neutralizing antibodies compared to the reported CCRL2 deficient murine models, we hypothesize that the ligand binding function of CCRL2 is dispensable for CXCL8 signaling in neutrophils. Finally, extensive profiling of CCRL2 expression on peripheral blood leukocytes revealed monocytes, dendritic cells (DC), and subpopulations of natural killer T (NKT) cells as additional targets, highlighting potential roles for CCRL2 in human cell types beyond neutrophils that warrants future investigation.

The immunological function of CXCR2 in the liver during sepsis

Background

The chemokine receptor CXCR2 and its ligands, especially CXCL8, are crucial mediators for the progression of liver inflammation and liver failure in sepsis. Neutrophils have the highest CXCR2 expression in mice and humans, and their activation via CXCL8 facilitates their migration to the inflamed liver for the clearance of the pathogens and, in turn, the inflammation.

Main body

In sepsis, the inflammatory insult causes extensive neutrophil migration to the liver that overwhelms the immune response. To compensate for the strong receptor activation, CXCR2 desensitizes, incapacitating the immune cells to efficiently clear pathogens, causing further life-threatening liver damage and uncontrolled pathogen spread.

Conclusion

CXCR2 function during infection strongly depends on the expressing cell type. It signals pro- and anti-inflammatory effects that may prompt novel cell-type-specific CXCR2-directed therapeutics.

CXCR1 and its downstream NF-κB inflammation signaling pathway as a key target of Guanxinning injection for myocardial ischemia/reperfusion injury

Guanxinning Injection (GXNI) is used clinically to treat cardiac injury, but its active components and mode of action remains unclear. Therefore, a myocardial ischemia/reperfusion injury (MIRI) model-based integrated strategy including function evaluation, RNA-seq analysis, molecular docking, and cellular thermal shift assay (CETSA) was employed to elucidate the effect and mechanism of GXNI and its main ingredient on cardiac injury. These results revealed that GXNI significantly improved cardiac dysfunction and myocardial injury in I/R mice. RNA-seq analysis clarified that CXCR1-mediated interleukin-8 pathway played a critical role in MIRI. Molecular docking screening identified danshensu (DSS) as the major active components of GXNI targeting CXCR1 protein, which was confirmed in an oxygen-glucose deprivation/reoxygenation-induced cardiomyocytes damage model showing that GXNI and DSS reduced the protein expression of CXCR1 and its downstream NF-κB, COX-2, ICAM-1 and VCAM-1. CETSA and isothermal dose-response fingerprint curves confirmed that DSS combined with CXCR1 in a dose-dependent manner. Furthermore, GXNI and DSS significantly decreased the expression levels of IL-6, IL-1β and TNF-α and the number of neutrophils in post I/R myocardial tissue. In conclusion, this study revealed that GXNI and its active components DSS exert inhibitory effects on inflammatory factor release and leukocyte infiltration to improve I/R-induced myocardial injury by down-regulating CXCR1-NF-κB-COX-2/ICAM-1/VCAM-1 pathway.

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.

Molecular cloning, characterization and expression analysis of CXCR3a and CXCR3b from Nile tilapia (Oreochromis niloticus)

The CXC chemokine receptors (CXCRs) are members of the seven transmembrane (7-TM) G-protein-coupled receptor superfamily that involves innate and adaptive immune systems. In this study, CXCR3a and CXCR3b from Nile tilapia (Oreochromis niloticus) were cloned and identified, designated as OnCXCR3a and OnCXCR3b. The open reading frames of OnCXCR3a and OnCXCR3b were 1074 and 1080 bp, encoding the predicted proteins of 357 and 359 amino acids, respectively. Multiple alignment analysis of OnCXCR3a- and OnCXCR3b-deduced protein sequences with the mammalian and bird sequences indicated the presence of typical structural features of chemokine receptors, including a 7-TM domain and conserved motifs. Quantitative real-time PCR analysis revealed that OnCXCR3a and OnCXCR3b were constitutively expressed in a wide range of tissues. When stimulated with Streptococcus agalactiae, Aeromonas hydrophila, polyinosinic:polycytidylic acid and lipopolysaccharide in vivo or in vitro on leukocytes, the mRNA levels of OnCXCR3a and OnCXCR3b were significantly upregulated. Overall, these results indicated that OnCXCR3s might be involved in host immune responses in Nile tilapia.

Improvement in insulin sensitivity and prevention of high fat diet-induced liver pathology using a CXCR2 antagonist

BACKGROUND

Liver pathology (LP) characteristic of non-alcoholic fatty acid disease (NAFLD)/non-alcoholic steatohepatitis (NASH) is a prevalent co-morbidity of type 2 diabetes (T2D). Accumulating evidence indicates that neutrophils driving insulin resistance (IR), including hepatic IR, precipitate T2D-associated NAFLD/NASH. We hypothesized that targeting neutrophil accumulation into insulin-sensitive tissues in mice using a CXCR2 antagonist under T2D-precipitating high fat diet (HFD) could improve insulin sensitivity and prevent the progression towards liver pathology reminiscent of NAFLD/NASH.

METHODS

Mice were age-matched and on standard rodent chow prior to 1:1 randomization into control and HFD formulated with the CXCR2 antagonist AZD5069 or with biologically inactive substitute. They were monitored for metabolic changes including insulin sensitivity using the hyperinsulinemic-euglycemic clamp and hepatic histopathologic evaluation in H&E-stained sections as well as via immunofluorescence microscopy of liver sections for leukocyte markers, collagen 1A1 formation, α-smooth muscle actin (SMA), and galectin-3 expression, for 16 weeks. Statistical tests used to determine significant differences among study groups and outcomes include Student's t-test, one-way ANOVA, repeated measures two-way ANOVA, and Fisher's exact test, depending on the analytical question.

RESULTS

Compared to mice on HFD, mice in the AZD5069-formulated HFD exhibited improved insulin sensitivity, a modest reduction in weight gain, and a significant improvement in LP and markers related to NAFLD/NASH. Mice in the AZD5069-formulated HFD also exhibited reduced neutrophil accumulation into the liver at the end of the 16 week study period.

CONCLUSIONS

These results show, for the first time, the effectiveness of a selective CXCR2 antagonist to improve insulin sensitivity, concomitantly preventing the progression towards LP characteristic of NAFLD/NASH. This represents a novel approach to target IR and developing LP under T2D-susceptible conditions using a single agent. Furthermore, our data extend the growing evidence in support of neutrophils as a leukocyte population that imprints and maintains a chronic inflammatory state in the progression of dysregulated metabolism in liver-specific co-morbid conditions.

The Importance of CXCL1 in the Physiological State and in Noncancer Diseases of the Oral Cavity and Abdominal Organs

CXCL1 is a CXC chemokine, CXCR2 ligand and chemotactic factor for neutrophils. In this paper, we present a review of the role of the chemokine CXCL1 in physiology and in selected major non-cancer diseases of the oral cavity and abdominal organs (gingiva, salivary glands, stomach, liver, pancreas, intestines, and kidneys). We focus on the importance of CXCL1 on implantation and placentation as well as on human pluripotent stem cells. We also show the significance of CXCL1 in selected diseases of the abdominal organs, including the gastrointestinal tract and oral cavity (periodontal diseases, periodontitis, Sjögren syndrome, Helicobacter pylori infection, diabetes, liver cirrhosis, alcoholic liver disease (ALD), non-alcoholic fatty liver disease (NAFLD), HBV and HCV infection, liver ischemia and reperfusion injury, inflammatory bowel disease (Crohn’s disease and ulcerative colitis), obesity and overweight, kidney transplantation and ischemic-reperfusion injury, endometriosis and adenomyosis).

Expression of Human Interleukin 8 in Mice Alters Their Natural Behaviors

Objective

To examine the effects of human interleukin (IL) 8 expression on mouse behavior.

Methods

A mouse line expressing human IL8 in the intervertebral discs (IVD) and cartilaginous tissues (hIL8⁺ ) was generated. Mouse spontaneous behaviors, including locomotion, climbing, rearing, grooming, eating, drinking, and immobility were recorded with a fully automatic, non-invasive platform.

Results

Distance traveled by the hIL8⁺ mice declined with age compared with control littermates, and male hIL8⁺ mice traveled a shorter distance than male controls and females of either genotype (p <0.05). The hIL8⁺ mice also spent less time in locomotion than control mice (p <0.01), and male hIL8⁺ mice spent the least amount of time and had lowest count in locomotion compared with the other 3 groups at 12 weeks of age or greater (p <0.05). The hIL8⁺ mice spent less time climbing than controls, and male mice spent less time climbing than female mice of the same genotype (p <0.01). The hIL8⁺ mice spent more time eating and less time drinking than controls, and all mice spent less time eating and more time drinking with increasing age. Finally, hIL8⁺ mice spent more time immobile than controls, and male hIL8⁺ mice spent more time immobile than any other group (p <0.05).

Conclusion

The hIL8⁺ mice, especially hIL8⁺ males, showed reduced ambulation and climbing. Mice showed age-related decrease in eating and increase in drinking and grooming time that was also influenced by expression of hIL8. These changes in natural behaviors in control mice are consistent with functional decline with age. Effects of hIL8 superimposed on the natural aging process could involve systemic (e.g., on the brain) and local (e.g., in the spine and joint tissues) mechanisms. Future exploration of these mechanisms might be productive.

The Importance of CXCL1 in Physiology and Noncancerous Diseases of Bone, Bone Marrow, Muscle and the Nervous System

This review describes the role of CXCL1, a chemokine crucial in inflammation as a chemoattractant for neutrophils, in physiology and in selected major non-cancer diseases. Due to the vast amount of available information, we focus on the role CXCL1 plays in the physiology of bones, bone marrow, muscle and the nervous system. For this reason, we describe its effects on hematopoietic stem cells, myoblasts, oligodendrocyte progenitors and osteoclast precursors. We also present the involvement of CXCL1 in diseases of selected tissues and organs including Alzheimer’s disease, epilepsy, herpes simplex virus type 1 (HSV-1) encephalitis, ischemic stroke, major depression, multiple sclerosis, neuromyelitis optica, neuropathic pain, osteoporosis, prion diseases, rheumatoid arthritis, tick-borne encephalitis (TBE), traumatic spinal cord injury and West Nile fever.

The CXCR1/CXCR2 Inhibitor Reparixin Alters the Development of Myelofibrosis in the Gata1 low Mice

A major role for human (h)CXCL8 (interleukin-8) in the pathobiology of myelofibrosis (MF) has been suggested by observations indicating that MF megakaryocytes express increased levels of hCXCL8 and that plasma levels of this cytokine in MF patients are predictive of poor patient outcomes. Here, we demonstrate that, in addition to high levels of TGF-β, the megakaryocytes from the bone marrow of the Gata1 low mouse model of myelofibrosis express high levels of murine (m)CXCL1, the murine equivalent of hCXCL8, and its receptors CXCR1 and CXCR2. Treatment with the CXCR1/R2 inhibitor, Reparixin in aged-matched Gata1 low mice demonstrated reductions in bone marrow and splenic fibrosis. Of note, the levels of fibrosis detected using two independent methods (Gomori and reticulin staining) were inversely correlated with plasma levels of Reparixin. Immunostaining of marrow sections indicated that the bone marrow from the Reparixin-treated group expressed lower levels of TGF-β1 than those expressed by the bone marrow from vehicle-treated mice while the levels of mCXCL1, and expression of CXCR1 and CXCR2, were similar to that of vehicle-treated mice. Moreover, immunofluorescence analyses performed on bone marrow sections from Gata1 low mice indicated that treatment with Reparixin induced expression of GATA1 while reducing expression of collagen III in megakaryocytes. These data suggest that in Gata1low mice, Reparixin reduces fibrosis by reducing TGF-β1 and collagen III expression while increasing GATA1 in megakaryocytes. Our results provide a preclinical rationale for further evaluation of this drug alone and in combination with current JAK inhibitor therapy for the treatment of patients with myelofibrosis.

Effects of systemic inflammation due to hepatic ischemia-reperfusion injury upon lean or obese visceral adipose tissue

Purpose:

To evaluate how the induction of liver damage by ischemia and reperfusion affects the adipose tissue of lean and obese mice.

Methods:

Lean and diet-induced obese mice were subjected to liver ischemia (30 min) followed by 6 h of reperfusion. The vascular stromal fraction of visceral adipose tissue was analyzed by cytometry, and gene expression was evaluated by an Array assay and by RT-qPCR. Intestinal permeability was assessed by oral administration of fluorescein isothiocyanate (FITC)-dextran and endotoxemia by serum endotoxin measurements using a limulus amebocyte lysate assay.

Results:

It was found that, after liver ischemia and reperfusion, there is an infiltration of neutrophils, monocytes, and lymphocytes, as well as an increase in the gene expression that encode cytokines, chemokines and their receptors in the visceral adipose tissue of lean mice. This inflammatory response was associated with the presence of endotoxemia in lean mice. However, these changes were not observed in the visceral adipose tissue of obese mice.

Conclusions:

Liver ischemia and reperfusion induce an acute inflammatory response in adipose tissue of lean mice characterized by an intense chemokine induction and leukocyte infiltration; however, inflammatory alterations are already present at baseline in the obese adipose tissue and liver ischemia and reperfusion do not injure further.

Interleukin-8: An evolving chemokine

Early in the 1980s several laboratories mistakenly reported that partially purified interleukin-1 (IL-1) was chemotactic for neutrophils. However, further investigations by us, revealed that our purified IL-1 did not have neutrophil chemotactic activity and this activity in the LPS-stimulated human monocyte conditioned media could clearly be separated from IL-1 activity on HPLC gel filtration. This motivated Teizo Yoshimura and Kouji Matsushima to purify the monocyte-derived neutrophil chemotactic factor (MDNCF), present in LPS conditioned media and molecularly clone the cDNA for MDNCF. They found that MDNCF protein (later renamed IL-8, and finally termed CXCL8) is first translated as a precursor form consisting of 99 amino acid residues and the signal peptide is then removed, leading to the secretion and processing of biologically active IL-8 of 72 amino acid form (residues 28-99). There are four cysteine residues forming two disulfide linkage and 14 basic amino acid residues which result in a very basic property for the binding of IL-8 to heparan sulfate-proteoglycan. The IL-8 gene consists of 4 exons and 3 introns. IL-8 is produced by various types of cells in inflammation. The 5'-flanking region of IL-8 gene contains several nuclear factor binding sites, and NF-κB in combination with AP-1 or C/EBP synergistically activates IL-8 gene in response to IL-1 and TNFα. Two receptors exist for IL-8, CXCR1 and CXCR2 in humans, which belong to γ subfamily of GTP binding protein (G-protein) coupled rhodopsin-like 7 transmembrane domain receptors. Rodents express CXCR2 and do not produce IL-8, but produce numerous homologues instead. Once IL-8 binds to the receptor, β and γ subunits of G-protein are released from Gα (Gαi2 in neutrophils) and activate PI3Kγ, PLCβ2/β3, PLA2 and PLD. Gαi2 inhibits adenyl cyclase to decrease cAMP levels. Small GTPases Ras/Rac/Rho/cdc42/Rap1, PKC and AKT (PKB) exist down-stream of β and γ subunits and regulate cell adhesion, actin polymerization, membrane protrusion, and eventually cell migration. PLCβ activation generates IP3 and induces Ca⁺⁺ mobilization, DAG generation to activate protein kinase C to lead granule exocytosis and respiratory burst. MDNCF was renamed interleukin 8 (IL-8) at the International Symposium on Novel Neutrophil Chemotactic Activating Polypeptides, London, UK in 1989. The discovery of IL-8 prompted us to also purify and molecularly clone the cDNA of MCAF/MCP-1 responsible for monocyte chemotaxis, and other groups to identify a large family of chemotactic cytokines capable of attracting other types of leukocytes. In 1992, most of the investigators contributing to the discovery of this new family of chemotactic cytokines gathered in Baden, Austria and agreed to name this family "chemokines" and subsequently established the CXCL/CCL and CXCR/CCR nomenclature. The discovery of chemokines resulted in solving the long-time enigma concerning the mechanism of cell type specific leukocyte infiltration into inflamed tissues and provided a molecular basis for immune and hematopoietic cell migration and interactions under physiological as well as pathological conditions. To our surprise based on its recently identified multifunctional activities, IL-8 has evolved from a neutrophil chemoattractant to a promising therapeutic target for a wide range of inflammatory and neoplastic diseases. IL-8 was initially characterized as a chemoattractant of neutrophils engaged in acute inflammation and then discovered to also be chemotactic for endothelial cells with a major role in angiogenesis. These two activities of IL-8 foster its stimulatory effect on tumor growth. This is abetted by recent additional discoveries showing that IL-8 has stimulatory effects on stem cells and can therefore directly promote the growth of receptor expressing cancer stem cells. IL-8 by interacting with bone marrow stem/progenitor cells has also the capacity to mobilize and release hematopoietic cells into the peripheral circulation. This includes the mobilization of neutrophilic myeloid-derived suppressor cells (N-MDSC) to infiltrate into tumors and thus further promotes the immune escape of tumors. Finally, the capacity of IL-8 to induce trans-differentiation of epithelial cancer cells into mesenchymal phenotype (EMT) increases the malignancy of tumors by promoting their metastatic spread and resistance to chemotherapeutics and cytotoxic immune cells. These observations have stimulated considerable current efforts to develop receptor antagonists for IL-8 and humanized anti-IL-8 antibody for the therapy of cancer, particularly in combination with immune checkpoint inhibitors, such as anti-PD-1/PD-L1 antibodies.

CXCL1: Gene, Promoter, Regulation of Expression, mRNA Stability, Regulation of Activity in the Intercellular Space

CXCL1 is one of the most important chemokines, part of a group of chemotactic cytokines involved in the development of many inflammatory diseases. It activates CXCR2 and, at high levels, CXCR1. The expression of CXCL1 is elevated in inflammatory reactions and also has important functions in physiology, including the induction of angiogenesis and recruitment of neutrophils. Due to a lack of reviews that precisely describe the regulation of CXCL1 expression and function, in this paper, we present the mechanisms of CXCL1 expression regulation with a special focus on cancer. We concentrate on the regulation of CXCL1 expression through the regulation of CXCL1 transcription and mRNA stability, including the involvement of NF-κB, p53, the effect of miRNAs and cytokines such as IFN-γ, IL-1β, IL-17, TGF-β and TNF-α. We also describe the mechanisms regulating CXCL1 activity in the extracellular space, including proteolytic processing, CXCL1 dimerization and the influence of the ACKR1/DARC receptor on CXCL1 localization. Finally, we explain the role of CXCL1 in cancer and possible therapeutic approaches directed against this chemokine.

In Vitro and In Vivo Models to Assess the Immune-Related Effects of Nanomaterials

The immunological safety of drugs, nanomaterials and contaminants is a central point in the regulatory evaluation and safety monitoring of working and public places and of the environment. In fact, anomalies in immune responses may cause diseases and hamper the physical and functional integrity of living organisms, from plants to human beings. In the case of nanomaterials, many experimental models are used for assessing their immunosafety, some of which have been adopted by regulatory bodies. All of them, however, suffer from shortcomings and approximations, and may be inaccurate in representing real-life responses, thereby leading to incomplete, incorrect or even misleading predictions. Here, we review the advantages and disadvantages of current nanoimmunosafety models, comparing in vivo vs. in vitro models and examining the use of animal vs. human cells, primary vs. transformed cells, complex multicellular and 3D models, organoids and organs-on-chip, in view of implementing a reliable and personalized nanoimmunosafety testing. The general conclusion is that the choice of testing models is key for obtaining reliable predictive information, and therefore special attention should be devoted to selecting the most relevant and realistic suite of models in order to generate relevant information that can allow for safer-by-design nanotechnological developments.

Hepatitis B virus middle surface antigen loss promotes clinical variant persistence in mouse models

Hepatitis B virus (HBV) middle surface antigen (MHBs) mutation or deletion occurs in patients with chronic HBV infection. However, the functional role of MHBs in HBV infection is still an enigma. Here, we reported that 7.33% (11/150) isolates of CHB patients had MHBs start codon mutations compared with 0.00% (0/146) in acute hepatitis B (AHB) patients. Interestingly, MHBs loss accounted for 11.88% (126/1061) isolates from NCBI GenBank, compared with 0.09% (1/1061) and 0.00% (0/1061) for HBV large surface antigen (LHBs) loss and HBV small surface antigen (SHBs) loss, respectively. One persistent HBV clone of genotype B (B56, MHBs loss) from a CHB patient was hydrodynamically injected into BALB/c mice. B56 persisted for >70 weeks in BALB/c mice, whereas B56 with restored MHBs (B56^M+) was quickly cleared within 28 days. Serum cytokine assays demonstrated that CXCL1, CXCL2, IL-6 and IL-33 were significantly increased during rapid HBV clearance in B56^M+ mice. Furthermore, the enhancers and promoters of B56 were proved to be required for B56 persistence in mice. Ablating MHBs expression improved the persistence of a new clone (HBV1.3, genotype B) which was recreated by using enhancers and promoters of B56. These data demonstrated that MHBs deletion can promote the persistence of specific HBV variants in a hydrodynamic mouse model. MHBs re-expression restored a rapid clearance of HBV, which was accompanied by cytokine responses including the elevation of CXCL1, CXCL2, IL-6 and IL-33.

Construction of heparin-based hydrogel incorporated with Cu5.4O ultrasmall nanozymes for wound healing and inflammation inhibition

Excessive production of inflammatory chemokines and reactive oxygen species (ROS) can cause a feedback cycle of inflammation response that has a negative effect on cutaneous wound healing. The use of wound-dressing materials that simultaneously absorb chemokines and scavenge ROS constitutes a novel 'weeding and uprooting' treatment strategy for inflammatory conditions. In the present study, a composite hydrogel comprising an amine-functionalized star-shaped polyethylene glycol (starPEG) and heparin for chemokine sequestration as well as Cu5.4O ultrasmall nanozymes for ROS scavenging (Cu5.4O@Hep-PEG) was developed. The material effectively adsorbs the inflammatory chemokines monocyte chemoattractant protein-1 and interleukin-8, decreasing the migratory activity of macrophages and neutrophils. Furthermore, it scavenges the ROS in wound fluids to mitigate oxidative stress, and the sustained release of Cu5.4O promotes angiogenesis. In acute wounds and impaired-healing wounds (diabetic wounds), Cu5.4O@Hep-PEG hydrogels outperform the standard-of-care product Promogram® in terms of inflammation reduction, increased epidermis regeneration, vascularization, and wound closure.

Self-sustaining IL-8 loops drive a prothrombotic neutrophil phenotype in severe COVID-19

Neutrophils provide a critical line of defense in immune responses to various pathogens, inflicting self-damage upon transition to a hyperactivated, procoagulant state. Recent work has highlighted proinflammatory neutrophil phenotypes contributing to lung injury and acute respiratory distress syndrome (ARDS) in patients with coronavirus disease 2019 (COVID-19). Here, we use state-of-the art mass spectrometry-based proteomics and transcriptomic and correlative analyses as well as functional in vitro and in vivo studies to dissect how neutrophils contribute to the progression to severe COVID-19. We identify a reinforcing loop of both systemic and neutrophil intrinsic IL-8 (CXCL8/IL-8) dysregulation, which initiates and perpetuates neutrophil-driven immunopathology. This positive feedback loop of systemic and neutrophil autocrine IL-8 production leads to an activated, prothrombotic neutrophil phenotype characterized by degranulation and neutrophil extracellular trap (NET) formation. In severe COVID-19, neutrophils directly initiate the coagulation and complement cascade, highlighting a link to the immunothrombotic state observed in these patients. Targeting the IL-8-CXCR-1/-2 axis interferes with this vicious cycle and attenuates neutrophil activation, degranulation, NETosis, and IL-8 release. Finally, we show that blocking IL-8-like signaling reduces severe acute respiratory distress syndrome of coronavirus 2 (SARS-CoV-2) spike protein-induced, human ACE2-dependent pulmonary microthrombosis in mice. In summary, our data provide comprehensive insights into the activation mechanisms of neutrophils in COVID-19 and uncover a self-sustaining neutrophil-IL-8 axis as a promising therapeutic target in severe SARS-CoV-2 infection.

Interferon gamma inhibits CXCL8-CXCR2 axis mediated tumor-associated macrophages tumor trafficking and enhances anti-PD1 efficacy in pancreatic cancer

Background

Pancreatic cancer (PC) is a common malignancy of the digestive system and is characterized by poor prognosis and early metastasis. Tumor immune escape plays an important role in PC progression. Programmed death 1 (PD1) blockade therapy is a promising treatment for patients with PC, but is yet to achieve significant clinical effects so far. Interferon gamma (IFN-γ) is a soluble dimeric cytokine that is closely associated with tumor immune surveillance and cytotoxicity. IFN-γ suppresses a variety of tumor-derived cytokines in PC, such as CXCL8. In the present study, we investigated the therapeutic efficacy of combined anti-PD1 and IFN-γ treatment in PC.

Methods

BxPC-3 and Panc-1 human PC cell lines were used to construct a murine PC model. Blood samples (n=44) and surgical resection specimens (n=36) from human patients with PC were also collected. χ² test, two-tailed unpaired t-test or Kaplan-Meier survival analysis was used to calculate p values.

Results

PD1/PD-L1 signaling was overexpressed in PC tumor-bearing mice. Anti-PD1 prevented tumor growth if initiated early after tumor inoculation; however, delayed anti-PD1 treatment showed limited benefit. Murine PC model had a preferential expansion of CXCR2⁺CD68⁺ macrophages, and these cells showed an immunosuppressive nature (M2 polarization). PC tumors overexpressed CXCL8 and tumor-derived CXCL8 deficiency prohibited the trafficking of CXCR2⁺CD68⁺ macrophages. IFN-γ suppressed the expression of tumor-derived CXCL8, and combined with IFN-γ treatment, delayed anti-PD1 treatment showed significant antitumor effects. Thus, we conclude that murine CXCR2⁺CD68⁺ macrophages traffic to PC tumors by tumor-derived CXCL8 and mediate local immunosuppression, which limits the efficacy of PD1 blockade therapy. IFN-γ suppresses tumor-derived CXCL8 and inhibits the tumor trafficking of CXCR2⁺CD68⁺ macrophages by blocking the CXCL8–CXCR2 axis to enhance anti-PD1 efficacy. Human PC also produces high levels of CXCL8. Patients with PC present elevated CXCR2 expression on peripheral and tumor-infiltrating CD68⁺ macrophages, which are associated with advanced tumor stage and poor prognosis.

Conclusion

Our findings suggest that IFN-γ is a translatable, therapeutic option to improve the efficacy of PD1 blockade therapy by preventing trafficking of CXCR2⁺CD68⁺ macrophages via blocking the CXCL8–CXCR2 axis.

IgE-Binding Monocytes Have an Enhanced Ability to Produce IL-8 (CXCL8) in Animals with Naturally Occurring Allergy

IL-8 is a potent chemokine that recruits neutrophils and basophils to promote inflammation in many species. IL-8 is produced by many cell types, including monocytes. In this study, we report a novel role for IgE-binding monocytes, a rare peripheral immune cell type, to promote allergic inflammation through IL-8 production in a horse model of natural IgE-mediated allergy. We developed a mAb with confirmed specificity for both recombinant and native equine IL-8 for flow cytometric analysis. Equine IL-8 was produced by CD14⁺/MHC class II⁺/CD16^- monocytes, including a subpopulation of IgE-binding monocytes, following stimulation with LPS. In addition, IgE cross-linking induced IL-8 production by both peripheral blood basophils and IgE-binding monocytes. IL-8 production was compared between healthy horses and those with a naturally occurring IgE-mediated skin allergy, Culicoides hypersensitivity. Allergic horses had significantly higher percentages of IL-8⁺ IgE-binding monocytes after IgE cross-linking. In contrast, frequencies of IL-8⁺ basophils after IgE cross-linking were similar in all horses, regardless of allergic disease, highlighting IgE-binding monocytes as a novel source of IL-8 during allergy. We concluded that IgE-binding monocytes from allergic individuals have an increased capacity for IL-8 production and likely contribute to the recruitment of innate immune cells during IgE-mediated allergy and promotion of inflammation during repeated allergen contact.

Neutrophil recruitment by chemokines Cxcl1/KC and Cxcl2/MIP2: Role of Cxcr2 activation and glycosaminoglycan interactions

Chemokines play a crucial role in combating microbial infection by recruiting blood neutrophils to infected tissue. In mice, the chemokines Cxcl1/KC and Cxcl2/MIP2 fulfill this role. Cxcl1 and Cxcl2 exist as monomers and dimers, and exert their function by activating the Cxcr2 receptor and binding glycosaminoglycans (GAGs). Here, we characterized Cxcr2 G protein and β-arrestin activities, and GAG heparan sulfate (HS) interactions of Cxcl1 and Cxcl2 and of the trapped dimeric variants. To understand how Cxcr2 and GAG interactions impact in vivo function, we characterized their neutrophil recruitment activity to the peritoneum, Cxcr2 and CD11b levels on peritoneal and blood neutrophils, and transport profiles out of the peritoneum. Cxcl2 variants compared with Cxcl1 variants were more potent for Cxcr2 activity. Native Cxcl1 compared with native Cxcl2 and dimers compared with native proteins bound HS with higher affinity. Interestingly, recruitment activity between native Cxcl1 and Cxcl2, between dimers, and between the native protein and the dimer could be similar or very different depending on the dose or the time point. These data indicate that peritoneal neutrophil recruitment cannot be solely attributed to Cxcr2 or GAG interactions, and that the relationship between recruited neutrophils, Cxcr2 activation, GAG interactions, and chemokine levels is complex and highly context dependent. We propose that the ability of Cxcl1 and Cxcl2 to reversibly exist as monomers and dimers and differences in their Cxcr2 activity and GAG interactions coordinate neutrophil recruitment and activation, which play a critical role for successful resolution of inflammation.

Hepatitis B-Induced IL8 Promotes Hepatocellular Carcinoma Venous Metastasis and Intrahepatic Treg Accumulation

Hepatitis B-associated hepatocellular carcinoma (HCC) is often accompanied by severe vascular invasion and portal vein tumor thrombus, leading to a poor prognosis. However, the underlying mechanism of this disease remains obscure. In this study, we demonstrate that the hepatitis B virus (HBV)-encoded gene HBx induces high IL8 production through MEK-ERK signal activation, leading to enhanced endothelial permeability to facilitate tumor vascular invasion. In a vascular metastatic model using a tail vein injection in a transgenic mouse with selective expression of human CXCR1 in the endothelium, activation of the IL8-CXCR1 cascade by overexpression of IL8 in tumor cells dramatically enhanced liver metastasis. Mechanistically, IL8 selectively induced GARP-latent-TGFβ in liver sinusoidal endothelial cells and subsequently provoked preferential regulatory T-cell polarization to suppress antitumor immunity. Collectively, these findings reveal a hepatitis B-associated IL8-CXCR1 signaling axis that mediates vascular invasion and local microenvironmental immune escape of HCC to induce intrahepatic metastasis, which may serve as potential therapeutic targets for HBV-associated HCC. SIGNIFICANCE: This study identifies a hepatitis B-induced IL8/CXCR1/TGFβ signaling cascade that suppresses antitumor immunity and enhances metastasis in hepatocellular carcinoma, providing new potential targets for therapeutic intervention.

Structural and functional analysis of Ccr1l1, a Rodentia-restricted eosinophil-selective chemokine receptor homologue

Mouse Ccr1l1 (Ccr1-like 1) encodes an orphan G-protein-coupled receptor (GPCR) with the highest homology to the inflammatory and highly promiscuous chemokine receptors Ccr1 and Ccr3 (70 and 50% amino acid identity, respectively). Ccr1l1 was first cloned in 1995, yet current knowledge of this putative chemokine receptor is limited to its gene organization and chromosomal localization. Here we report that Ccr1l1 is a Rodentia-specific gene selectively expressed in eosinophils. However, eosinophil phenotypes, development, and responsiveness to chemokines were all normal in naïve Ccr1l1 knockout mice. We demonstrate for the first time that recombinant Ccr1l1 is expressed on the plasma membrane of transfected cells and contains an extracellular N terminus and an intracellular C terminus, consistent with GPCR topology. Using receptor internalization, β-arrestin recruitment, calcium flux, and chemotaxis assays, we excluded all 37 available mouse chemokines, including Ccr1 ligands, and two viral chemokines as Ccr1l1 ligands, and demonstrated that mouse Ccr1, but not Ccr1l1, exhibits constitutive signaling activity. However, sequence analysis and structural modeling revealed that Ccr1l1 is well equipped to act as a classical signaling GPCR, with N-terminal sulfotyrosines as the only signaling and chemokine-binding determinant absent in Ccr1l1. Hereof, we show that a sulfatable N-terminal Ccr1 Y¹⁸ residue is essential for chemotaxis and calcium responses induced by Ccl3 and Ccl9/10, but substituting the corresponding Ccr1l1 F¹⁹ residue with tyrosine failed to confer responsiveness to Ccr1 ligands. Although Ccr1l1 remains an extreme outlier in the chemokine receptor family, our study supports that it might respond to unidentified mouse chemokine ligands in eosinophil-driven immune responses.

Transcriptomic Analysis of Rat Macrophages

The laboratory rat is widely used as a model for human diseases. Many of these diseases involve monocytes and tissue macrophages in different states of activation. Whilst methods for in vitro differentiation of mouse macrophages from embryonic stem cells (ESC) and bone marrow (BM) are well established, these are lacking for the rat. The gene expression profiles of rat macrophages have also not been characterised to the same extent as mouse. We have established the methodology for production of rat ESC-derived macrophages and compared their gene expression profiles to macrophages obtained from the lung and peritoneal cavity and those differentiated from BM and blood monocytes. We determined the gene signature of Kupffer cells in the liver using rats deficient in macrophage colony stimulating factor receptor (CSF1R). We also examined the response of BM-derived macrophages to lipopolysaccharide (LPS). The results indicate that many, but not all, tissue-specific adaptations observed in mice are conserved in the rat. Importantly, we show that unlike mice, rat macrophages express the CSF1R ligand, colony stimulating factor 1 (CSF1).

Nile tilapia CXCR4, the receptor of chemokine CXCL12, is involved in host defense against bacterial infection and chemotactic activity

CXC chemokine receptor 4 (CXCR4), a member of seven-transmembrane (7-TM) G-protein-coupled receptor superfamily, is the receptor of the CXC chemokine ligand 12 (CXCL12), and plays important roles in host defense and inflammation. In the current study, we cloned and identified a homolog of CXCR4 from Nile tilapia (Oreochromis niloticus), designated as OnCXCR4. The open reading frame of OnCXCR4 is 1149 bp encoding a peptide of 382 amino acids, and the predicted molecular weight is 42.65 kDa OnCXCR4 shares common features of CXCR4 family, including a 7-TM domain and a characteristic CXC motif (containing CYC). Expression analysis showed that OnCXCR4 constitutively expresses in various tested tissues of Nile tilapia, with the highest level in the anterior kidney. When stimulated with Streptococcus agalactiae, Aeromonas hydrophila, Poly(I:C), or LPS in vivo and in vitro, the expression of OnCXCR4 was significantly regulated. AMD3100, a CXCR4 antagonist, could not only inhibit the chemotactic activity of the recombinant OnCXCL12 protein on the leukocytes from anterior kidney, but also reduce the expression of OnCXCR4 significantly. Taken together, these results of our study above indicate that OnCXCR4 may play important roles in host defense against bacterial infectionin in Nile tilapia, and being a receptor of OnCXCL12 to exert functions.

IL-8 exacerbates alcohol-induced fatty liver disease via the Akt/HIF-1α pathway in human IL-8-expressing mice

Alcoholic fatty liver disease (AFLD) is a disease that causes liver damage due to chronic heavy drinking. AFLD is related to lipid accumulation in liver cells caused by alcohol intake. Interleukin-8 (IL-8) is an inflammatory cytokine associated with chemotaxis (deletion in mice) that has robust effects on the occurrence and development of disease by activating related signal transduction pathways to promote inflammation and cell proliferation. There is significantly increased IL-8 expression in liver disease, which may be related to the pathogenesis of AFLD. In this study, we used hydrodynamic injection to deliver the liver-specific expression vector pLIVE-hIL-8 into mice. We found that hIL-8 can exacerbate alcohol-induced fatty liver disease via the Akt/HIF-1α pathway. Exacerbated liver lipid degeneration in mice, which is characterized by excessive accumulation of triglycerides, and liver damage markers were significantly increased. Moreover, hIL-8 could increase the alcohol-induced release of ROS in fatty liver caused by alcohol and exacerbate fatty liver disease. The expression of liver lipid metabolism-related gene sterol regulatory element-binding protein-1c (SREBP-1c) was increased. Furthermore, the expression of peroxisome proliferator-activated receptor alpha (PPARα), which is related to liver fatty acid oxidation, was decreased. The findings obtained in this study of hIL-8 will help identify a potential target for the clinical treatment of AFLD.

Enhanced IgG1 -mediated antibody response towards thymus-dependent immunization in CXCR1-deficient mice

Background

Chemokine receptors and their corresponding ligands are key players of immunity by regulation of immune cell differentiation and migration. CXCR1 is a high‐affinity receptor for CXCL8. Differential expression of CXCR1 is associated with a variety of human pathologies including cancer and inflammatory diseases. While various studies have highlighted the importance of CXCR1‐mediated CXCL8‐sensing for neutrophil trafficking and function, its role in B‐cell responses remains unsolved. Therefore, our aim was to investigate innate and adaptive antibody responses in CXCR1‐deficient mice.

Methods

Cell populations of the spleen and the peritoneal cavity were identified and quantified via flow cytometry. To investigate thymus‐independent (TI) and thymus‐dependent (TD) antibody responses, mice were immunized intraperitoneally with TNP‐Ficoll, Pneumovax23, and TNP‐Chicken Gamma Globulin. Mice were bled before as well as 7 and 14 days after vaccination to collect serum. Serum antibody levels overtime were analyzed according to their specificity by enzyme‐linked immunosorbent assay. B‐1 cell functionality was examined by IL‐5/IL‐5Rα‐dependent stimulation of peritoneal and splenic cells in vitro. To analyze CXCR1/2‐expression, CD19⁺ splenocytes were enriched by magnetic‐activated cell sorting before isolation of total RNA contents, followed by reverse transcription and real‐time polymerase chain reaction.

Results

The distribution of natural B‐1 cell populations was disturbed in the absence of CXCR1, while their responsiveness towards TI antigens and in vitro stimulation remained functional. Besides, CXCR1‐deficiency was accompanied by increased frequencies of follicular B‐2 cells in the spleen. Interestingly, these mice produced elevated levels of antigen‐specific IgG₁ upon TD immunization and harbored a significantly enlarged proportion of CXCR5‐expressing T helper (H) cells. CXCR1‐expression was detectable in CD19⁺ splenocytes derived from wild‐type, but not CXCR1‐deficient mice.

Conclusion

Our data demonstrate a previously unknown relevance of CXCR1 for the production of specific IgG₁ in response to vaccination. These findings identify CXCR1 as a promising candidate for future studies on the regulation of adaptive antibody responses.

Differential contribution of bone marrow-derived infiltrating monocytes and resident macrophages to persistent lung inflammation in chronic air pollution exposure

Chronic exposure to particulate matter < 2.5µ (PM_2.5) has been linked to cardiopulmonary disease. Tissue-resident (TR) alveolar macrophages (AΦ) are long-lived, self-renew and critical to the health impact of inhalational insults. There is an inadequate understanding of the impact of PM_2.5 exposure on the nature/time course of transcriptional responses, self-renewal of AΦ, and the contribution from bone marrow (BM) to this population. Accordingly, we exposed chimeric (CD45.2/CD45.1) mice to concentrated PM_2.5 or filtered air (FA) to evaluate the impact on these end-points. PM_2.5 exposure for 4-weeks induced an influx of BM-derived monocytes into the lungs with no contribution to the overall TR-AΦ pool. Chronic (32-weeks) PM_2.5 exposure on the other hand while associated with increased recruitment of BM-derived monocytes and their incorporation into the AΦ population, resulted in enhanced apoptosis and decreased proliferation of TR-AΦ. RNA-seq analysis of isolated TR-AΦ and BM-AΦ from 4- and 32-weeks exposed mice revealed a unique time-dependent pattern of differentially expressed genes. PM_2.5 exposure resulted in altered histological changes in the lungs, a reduced alveolar fraction which corresponded to protracted lung inflammation. Our findings suggest a time-dependent entrainment of BM-derived monocytes into the AΦ population of PM_2.5 exposed mice, that together with enhanced apoptosis of TR-AΦ and reorganization of transcriptional responses, could collectively contribute to the perpetuation of chronic inflammation.

Sex differences in the acute and subchronic lung inflammatory responses of mice to nickel nanoparticles

Nickel nanoparticles (NiNPs) are increasingly used in nanotechnology applications, yet information on sex differences in NiNP-induced lung disease is lacking. The goal of this study was to explore mechanisms of susceptibility between male and female mice after acute or subchronic pulmonary exposure to NiNPs. For acute exposure, male and female mice received a single dose of NiNPs with or without LPS by oropharyngeal aspiration and were necropsied 24 h later. For subchronic exposure, mice received NiNPs with or without LPS six times over 3 weeks prior to necropsy. After acute exposure to NiNPs and LPS, male mice had elevated cytokines (CXCL1 and IL-6) and more neutrophils in bronchoalveolar lavage fluid (BALF), along with greater STAT3 phosphorylation in lung tissue. After subchronic exposure to NiNPs and LPS, male mice exhibited increased monocytes in BALF. Moreover, subchronic exposure of male mice to NiNP only induced higher CXCL1 and CCL2 in BALF along with increased alveolar infiltrates and CCL2 in lung tissue. STAT1 in lung tissue was induced by subchronic exposure to NiNPs in females but not males. Males had a greater induction of IL-6 mRNA in liver after acute exposure to NiNPs and LPS, and greater CCL2 mRNA in liver after subchronic NiNP exposure. These data indicate that susceptibility of males to acute lung inflammation involves enhanced neutrophilia with increased CXCL1 and IL-6/STAT3 signaling, whereas susceptibility to subchronic lung inflammation involves enhanced monocytic infiltration with increased CXCL1 and CCL2. STAT transcription factors appear to play a role in these sex differences. This study demonstrates sex differences in the lung inflammatory response of mice to NiNPs that has implications for human disease.

Multiple Roles for Chemokines in Neutrophil Biology

Chemokines are recognized as the most critical mediators for selective neutrophil recruitment during inflammatory conditions. Furthermore, they are considered fundamental regulators of neutrophil mobilization from the bone marrow (BM) to the bloodstream and for their homing back at the end of their life for apoptosis and clearance. However, chemokines are also important mediators of neutrophil effector functions including oxidative burst, degranulation, neutrophil extracellular trap (NET)osis, and production of inflammatory mediators. Neutrophils have been historically considered as a homogeneous population. In recent years, several maturation stages and subsets with different phenotypic profiles and effector functions were described both in physiological and pathological conditions such as infections, autoimmunity, and cancer. The aim of this review is to give an overview of the current evidence regarding the role of chemokines and chemokine receptors in neutrophil biology, including their possible role in neutrophil maturation, differentiation, and in defining emerging neutrophil subsets.

Neutralization of TNF-α and IL-1β Regulates CXCL8 Production through CXCL8/CXCR1 Axis in Macrophages during Staphylococcus aureus Infection

Anti-cytokine therapy is widely acknowledged as an anti-inflammatory technique to treat varied infectious diseases. TNF-α and IL-1β are major cytokines that regulate every aspect of the inflammatory process. However, the effects of single or dual cytokine neutralization on S. aureus mediated CXCL8 secretion and CXCR1 expression in murine peritoneal macrophages remained noninvestigated. Thus we aimed to explore the effects of kinetic-dose dependent neutralization of TNF-α and IL-1β using specific anti-cytokine antibodies and its influential impact on the CXCL8/CXCR1 axis at different stages of S. aureus (30, 60, and 90 min) infection. The murine peritoneal macrophages were isolated and infected with viable S. aureus followed by subsequent addition of anti-TNF-α and anti-IL-1β into the medium. The treated cells were centrifuged and lysate and supernatant collected for various experiments. The ROS generation was measured and cytokine production was estimated by ELISA. The expression of TNFR1, IL-1R, CXCR1, signaling molecules (NF-κB and JNK) were evaluated by Western blot. The role of single or dual cytokine neutralization on intracellular bacterial phagocytosis had also been analyzed by confocal microscopy. Dual cytokine neutralization significantly suppressed ROS, cytokines, CXCL8 secretion, and intracellular bacterial count compared to single cytokine neutralization and it was more apparent at 90 min post S. aureus infection. There was a drastic reduction in TNFR1, IL-1R, and CXCR1 expression on macrophage surface due to reduced expression of downstream signaling molecules, NF-κB and JNK. Hence dual cytokine neutralization was more effectual compared to single cytokine neutralization in the downregulation of S. aureus induced CXCR1 expression.

Metformin modulates immune cell infiltration into the kidney during unilateral ureteral obstruction in mice

Metformin is today the first choice treatment for type‐2 diabetes, but has also protective effects in several renal disease models. Previously, we have demonstrated that the protective effects in response to unilateral ureteral obstruction (UUO) are independent of organic cation transporters (OCTs), the transporters responsible for the metformin uptake into the renal cells. The mechanisms behind the renoprotective effects are incompletely understood, but our previous results indicate that the renoprotective effects at least partly could be dependent on actions of metformin outside the renal cells. In this study, we investigate whether the renoprotective effects of metformin can be mediated via systemic immunomodulatory actions. We demonstrated that metformin can affect the immune system in the kidney as well as in the peripheral blood and spleen following UUO. UUO kidneys showed infiltration of immune cells including monocytes, B cells, and T cells, but metformin limited infiltration of all cell types. UUO animals had increased spleen sizes, but this increase was attenuated by metformin. Metformin treatment surprisingly resulted in a higher proportion of monocytes with infiltratory capacity 7 days after UUO. Other studies have suggested that metformin regulates monocyte maturation through signal transducer and activator of transcription 3 (STAT3) activation, as also indicated by our results. In conclusion, our results demonstrate that metformin limits the infiltration of immune cells into the kidney, as well as modulates immune cell composition at a systemic level.