Expression of CXCL16 in human T cells

Role of Non-Coding RNAs in Post-Transcriptional Regulation of Lung Diseases

Non-coding RNAs (ncRNAs), notably microRNAs (miRNAs) and long noncoding RNAs (lncRNAs), have recently gained increasing consideration because of their versatile role as key regulators of gene expression. They adopt diverse mechanisms to regulate transcription and translation, and thereby, the function of the protein, which is associated with several major biological processes. For example, proliferation, differentiation, apoptosis, and metabolic pathways demand fine-tuning for the precise development of a specific tissue or organ. The deregulation of ncRNA expression is concomitant with multiple diseases, including lung diseases. This review highlights recent advances in the post-transcriptional regulation of miRNAs and lncRNAs in lung diseases such as asthma, chronic obstructive pulmonary disease, cystic fibrosis, and idiopathic pulmonary fibrosis. Further, we also discuss the emerging role of ncRNAs as biomarkers as well as therapeutic targets for lung diseases. However, more investigations are required to explore miRNAs and lncRNAs interaction, and their function in the regulation of mRNA expression. Understanding these mechanisms might lead to early diagnosis and the development of novel therapeutics for lung diseases.

Innate-like Gene Expression of Lung-resident Memory CD8+ T-cells During Experimental Human Influenza: A Clinical Study

RATIONALE

Suboptimal vaccine immunogenicity and antigenic mismatch, compounded by poor uptake, means that influenza remains a major global disease. T-cells recognising peptides derived from conserved viral proteins could enhance vaccine-induced cross-strain protection.

OBJECTIVES

To investigate the kinetics, phenotypes and function of influenza virus-specific CD8+ resident-memory T-cells (Trm) in the lower airway and infer the molecular pathways associated with their response to infection in vivo.

METHODS

Healthy volunteers, aged 18-55, were inoculated intranasally with influenza A(H1N1)2009. Blood, upper and (in a subgroup) lower airway samples were obtained throughout infection. Symptoms were assessed using self-reported diaries and nasal viral load by qPCR. T-cell responses were analysed by three-colour FluoroSpot, flow cytometry with MHC I-peptide tetramers and RNAseq, with candidate markers confirmed using immunohistochemistry of endobronchial biopsies.

MEASUREMENTS AND MAIN RESULTS

Following challenge, 57% of participants became infected. Pre-existing influenza-specific CD8+ T-cells in blood correlated strongly with reduced viral load, which peaked at day 3. Influenza-specific CD8+ T-cells in BAL were highly enriched and predominantly expressed the Trm markers CD69 and CD103. Comparison between pre-infection CD8+ T-cells in BAL and blood by RNAseq revealed 3928 differentially expressed genes, including all major Trm cell markers. However, gene-set enrichment analysis of BAL CD8+ T-cells showed primarily innate cell-related pathways and, during infection, included upregulation of innate chemokines (Cxcl1, Cxcl10 and Cxcl16) that were also expressed by CD8+ cells in bronchial tissues.

CONCLUSIONS

CD8+ Trm cells in the human lung display innate-like gene and protein expression that demonstrates blurred divisions between innate and adaptive immunity. Clinical trial registration available at www.clinicaltrials.gov, ID: NCT02755948.

Identification of Novel Biomarker for Early Detection of Diabetic Nephropathy

Diabetic nephropathy (DN) is one of the most common complications of diabetes mellitus. After development of DN, patients will progress to end-stage renal disease, which is associated with high morbidity and mortality. Here, we developed early-stage diagnostic biomarkers to detect DN as a strategy for DN intervention. For the DN model, Zucker diabetic fatty rats were used for DN phenotyping. The results revealed that DN rats showed significantly increased blood glucose, blood urea nitrogen (BUN), and serum creatinine levels, accompanied by severe kidney injury, fibrosis and microstructural changes. In addition, DN rats showed significantly increased urinary excretion of kidney injury molecule-1 (KIM-1) and neutrophil gelatinase-associated lipocalin (NGAL). Transcriptome analysis revealed that new DN biomarkers, such as complementary component 4b (C4b), complementary factor D (CFD), C-X-C motif chemokine receptor 6 (CXCR6), and leukemia inhibitory factor (LIF) were identified. Furthermore, they were found in the urine of patients with DN. Since these biomarkers were detected in the urine and kidney of DN rats and urine of diabetic patients, the selected markers could be used as early diagnosis biomarkers for chronic diabetic nephropathy.

Role of inflammatory chemokines in hypertension

Hypertension is associated with immune cells activation and their migration into the kidney, vasculature, heart and brain. These inflammatory mechanisms are critical for blood pressure regulation and mediate target organ damage, creating unique novel targets for pharmacological modulation. In response to angiotensin II and other pro-hypertensive stimuli, the expression of several inflammatory chemokines and their receptors is increased in the target organs, mediating homing of immune cells. In this review, we summarize the contribution of key inflammatory chemokines and their receptors to increased accumulation of immune cells in target organs and effects on vascular dysfunction, remodeling, oxidative stress and fibrosis, all of which contribute to blood pressure elevation. In particular, the role of CCL2, CCL5, CXCL8, CXCL9, CXCL10, CXCL11, CXCL16, CXCL1, CX3CL1, XCL1 and their receptors in the context of hypertension is discussed. Recent studies have tested the efficacy of pharmacological or genetic targeting of chemokines and their receptors on the development of hypertension. Promising results indicate that some of these pathways may serve as future therapeutic targets to improve blood pressure control and prevent target organ consequences including kidney failure, heart failure, atherosclerosis or cognitive impairment.

The Role of Autophagy and the Chemokine (C-X-C Motif) Ligand 16 During Acute Lung Injury in Mice

Background

Acute lung injury (ALI) is responsible for mortality in hospitalized patients. Autophagy can negatively regulate inflammatory response, and CXCL16 (chemokine (C-X-C motif) ligand 16) is a kind of chemokine, which is closely related to the inflammatory response. However, the relationship between autophagy and CXCL16 in ALI is still unclear. This study aimed to investigate the role of autophagy and chemokine CXCL16 in ALI in mice.

Material/Methods

Thirty-two male C57BL/6 mice were divided into four groups. The control group (C group) was given normal saline through intraperitoneal injection. The L group was given LPS (lipopolysaccharide) at 30 mg/kg to construct an ALI model. The 3-MA group received an intraperitoneal injection of inhibitor of autophagy 3-methyladenine at 15 mg/kg, 30 minutes before LPS injection. The anti-CXCL16 group was given 20 mg/kg of CXCL16 monoclonal antibody 30 minutes before the LPS injection.

Results

In the 3-MA Group, the level of histological analysis, lung wet/dry ratio, total protein of BAL (bronchoalveolar lavage fluid) and TNF-α level were higher than the L group (p<0.05), the level of autophagy was lower than the L group (p<0.05), and the level of CXCL16 was higher than the L group (p<0.05). In the anti-CXCL16 group, the level of histological analysis, lung wet/dry ratio, BAL protein, and TNF-α level were declined compared to the L group (p<0.05), but there was no statistically significant difference in expression of CXCL16 detected by ELISA between the anti-CXCL16 group and the L group (p>0.05).

Conclusions

Autophagy played a protective role in ALI induced by LPS in mice. Autophagy could regulate the level of CXCL16. The chemokine CXCL16 could exacerbate ALI.

Long Noncoding RNAs and mRNA Regulation in Peripheral Blood Mononuclear Cells of Patients with Chronic Obstructive Pulmonary Disease

Background

Inflammation plays a pivotal role in the pathogenesis of chronic obstructive pulmonary disease (COPD). We evaluated the lncRNA and mRNA expression profile of peripheral blood mononuclear cells (PBMCs) from healthy nonsmokers, smokers without airflow limitation, and COPD patients.

Methods

lncRNA and mRNA profiling of PBMCs from 17 smokers and 14 COPD subjects was detected by high-throughput microarray. The expression of dysregulated lncRNAs was validated by qPCR. The lncRNA targets in dysregulated mRNAs were predicted and the GO enrichment was analyzed. The regulatory role of lncRNA ENST00000502883.1 on CXCL16 expression and consequently the effect on PBMC recruitment were investigated by siRNA knockdown and chemotaxis analysis.

Results

We identified 158 differentially expressed lncRNAs in PBMCs from COPD subjects compared with smokers. The dysregulated expression of 5 selected lncRNAs NR_026891.1 (FLJ10038), ENST00000502883.1 (RP11-499E18.1), HIT000648516, XR_429541.1, and ENST00000597550.1 (CTD-2245F17.3), was validated. The GO enrichment showed that leukocyte migration, immune response, and apoptosis are the main enriched processes that previously reported to be involved in the pathogenesis of COPD. The regulatory role of ENST00000502883.1 on CXCL16 expression and consequently the effect on PBMC recruitment was confirmed.

Conclusion

This study may provide clues for further studies targeting lncRNAs to control inflammation in COPD.

Equine Arteritis Virus Has Specific Tropism for Stromal Cells and CD8+ T and CD21+ B Lymphocytes but Not for Glandular Epithelium at the Primary Site of Persistent Infection in the Stallion Reproductive Tract

Equine arteritis virus (EAV) has a global impact on the equine industry as the causative agent of equine viral arteritis (EVA), a respiratory, systemic, and reproductive disease of equids. A distinctive feature of EAV infection is that it establishes long-term persistent infection in 10 to 70% of infected stallions (carriers). In these stallions, EAV is detectable only in the reproductive tract, and viral persistence occurs despite the presence of high serum neutralizing antibody titers. Carrier stallions constitute the natural reservoir of the virus as they continuously shed EAV in their semen. Although the accessory sex glands have been implicated as the primary sites of EAV persistence, the viral host cell tropism and whether viral replication in carrier stallions occurs in the presence or absence of host inflammatory responses remain unknown. In this study, dual immunohistochemical and immunofluorescence techniques were employed to unequivocally demonstrate that the ampulla is the main EAV tissue reservoir rather than immunologically privileged tissues (i.e., testes). Furthermore, we demonstrate that EAV has specific tropism for stromal cells (fibrocytes and possibly tissue macrophages) and CD8⁺ T and CD21⁺ B lymphocytes but not glandular epithelium. Persistent EAV infection is associated with moderate, multifocal lymphoplasmacytic ampullitis comprising clusters of B (CD21⁺) lymphocytes and significant infiltration of T (CD3⁺, CD4⁺, CD8⁺, and CD25⁺) lymphocytes, tissue macrophages, and dendritic cells (Iba-1⁺ and CD83⁺), with a small number of tissue macrophages expressing CD163 and CD204 scavenger receptors. This study suggests that EAV employs complex immune evasion mechanisms that warrant further investigation.IMPORTANCE The major challenge for the worldwide control of EAV is that this virus has the distinctive ability to establish persistent infection in the stallion's reproductive tract as a mechanism to ensure its maintenance in equid populations. Therefore, the precise identification of tissue and cellular tropism of EAV is critical for understanding the molecular basis of viral persistence and for development of improved prophylactic or treatment strategies. This study significantly enhances our understanding of the EAV carrier state in stallions by unequivocally identifying the ampullae as the primary sites of viral persistence, combined with the fact that persistence involves continuous viral replication in fibrocytes (possibly including tissue macrophages) and T and B lymphocytes in the presence of detectable inflammatory responses, suggesting the involvement of complex viral mechanisms of immune evasion. Therefore, EAV persistence provides a powerful new natural animal model to study RNA virus persistence in the male reproductive tract.

Allelic Variation in CXCL16 Determines CD3+ T Lymphocyte Susceptibility to Equine Arteritis Virus Infection and Establishment of Long-Term Carrier State in the Stallion

Equine arteritis virus (EAV) is the causative agent of equine viral arteritis (EVA), a respiratory, systemic, and reproductive disease of horses and other equid species. Following natural infection, 10-70% of the infected stallions can become persistently infected and continue to shed EAV in their semen for periods ranging from several months to life. Recently, we reported that some stallions possess a subpopulation(s) of CD3+ T lymphocytes that are susceptible to in vitro EAV infection and that this phenotypic trait is associated with long-term carrier status following exposure to the virus. In contrast, stallions not possessing the CD3+ T lymphocyte susceptible phenotype are at less risk of becoming long-term virus carriers. A genome wide association study (GWAS) using the Illumina Equine SNP50 chip revealed that the ability of EAV to infect CD3+ T lymphocytes and establish long-term carrier status in stallions correlated with a region within equine chromosome 11. Here we identified the gene and mutations responsible for these phenotypes. Specifically, the work implicated three allelic variants of the equine orthologue of CXCL16 (EqCXCL16) that differ by four non-synonymous nucleotide substitutions (XM_00154756; c.715 A → T, c.801 G → C, c.804 T → A/G, c.810 G → A) within exon 1. This resulted in four amino acid changes with EqCXCL16S (XP_001504806.1) having Phe, His, Ile and Lys as compared to EqCXL16R having Tyr, Asp, Phe, and Glu at 40, 49, 50, and 52, respectively. Two alleles (EqCXCL16Sa, EqCXCL16Sb) encoded identical protein products that correlated strongly with long-term EAV persistence in stallions (P<0.000001) and are required for in vitro CD3+ T lymphocyte susceptibility to EAV infection. The third (EqCXCL16R) was associated with in vitro CD3+ T lymphocyte resistance to EAV infection and a significantly lower probability for establishment of the long-term carrier state (viral persistence) in the male reproductive tract. EqCXCL16Sa and EqCXCL16Sb exert a dominant mode of inheritance. Most importantly, the protein isoform EqCXCL16S but not EqCXCL16R can function as an EAV cellular receptor. Although both molecules have equal chemoattractant potential, EqCXCL16S has significantly higher scavenger receptor and adhesion properties compared to EqCXCL16R.

CXCL16 in Vascular Pathology Research: from Macro Effects to microRNAs

Chemokines and their receptors have become significant factors in atherosclerosis research. CXCL16 is a multifunctional agent located on a separate locus to all other known chemokines and binds only to its "unique" receptor named CXCR6. As a scavenger receptor, adhesion molecule, and chemokine, it quickly became an interesting target in atherosclerosis research as all its functions have a role in vascular pathology. The investigation of the role of CXCL16 in atherosclerosis, although shown in in vitro studies, animal knockout models, and CXCL16 gene polymorphisms, haplotypes, and circulating levels, still shows puzzling results. Genetic and epigenetic studies have just scratched the surface of research necessary for a better assessment of the significance and perspective of this marker in plaque development and progression. In this review, we will summarize current knowledge about CXCL16 in atherosclerosis. Additionally, we will point out the importance of bioinformatics tools for the detection of potentially new CXCL16 regulatory networks through microRNA activity. This review aims to provide a better understanding of the underlying mechanisms, define more specific biomarkers, and discover new therapeutic targets.

CXCL16 in kidney and cardiovascular injury

CXC chemokine ligand 16 (CXCL16) is a CXC soluble chemokine, an adhesion molecule and a cell surface scavenger receptor. CXCL16 regulates inflammation, tissue injury and fibrosis. Parenchymal renal cells, vascular wall cells, leukocytes and platelets express and/or release CXCL16 under the regulation of inflammatory mediators. CXCL16 expression is increased in experimental and human nephropathies. Targeting CXCL16 protected from experimental glomerular injury or interstitial fibrosis. Conflicting results were reported for experimental cardiovascular injury. High circulating CXCL16 levels are associated to human kidney and cardiovascular disease and urinary CXCL16 may increase in kidney injury. In conclusion, mounting evidence suggests a role of CXCL16 in kidney and cardiovascular disease. However, a better understanding is still required before exploring CXCL16 targeting in the clinic.

Plasmacytoid dendritic cell response to CpG ODN correlates with CXCL16 expression and is inhibited by ox-LDL

Structurally distinct classes of synthetic CpG oligonucleotides (ODN) differentially activate human immune cells. K-type ODN trigger plasmacytoid dendritic cells (pDCs) to differentiate and produce TNFα. In contrast, D-type ODN stimulate large amounts of IFNα secretion from pDCs. The cell-surface receptor CXCL16 was previously shown to influence the nature and specificity of CpG ODN-induced immune activation. Here, we evaluated the expression and function of CXCL16 on pDC from healthy volunteers. We report that increased CXCL16 expression correlated with enhanced in vitro response exclusively to D-type CpG ODN. Conversely, enzymatic digestion of the receptor resulted in a decrease in IFNα production. Moreover, ox-LDL presence significantly inhibited D-ODN mediated IFNα production by pDCs. Coculture of enriched pDCs with the CXCR6 expressing Jurkat T cells decreased the activation threshold of these cells responding to D-ODN, suggesting that CXCL16/CXCR6 interaction may play an important role in modifying the response of pDCs to environmental danger signals.

Associations of CXCL16/CXCR6 with carotid atherosclerosis in patients with metabolic syndrome

BACKGROUND & AIMS

Chemokine CXC ligand 16 (CXCL16) has chemokine, adhesion molecule and scavenger receptor functions involving the immune function. Atherosclerosis is an inflammatory disease. We aimed to study the association of chemokine CXCL16/CXCR6 and carotid atherosclerosis in patients with metabolic syndrome.

METHODS

Carotid ultrasonography was determined in 30 patients with metabolic syndrome and 30 controls. The mRNA levels of CXCL6/CXCR6 were detected by real-time RT-PCR. The activation of T cells and expression of CXCR6 in T lymphocyte cells and natural killer T (NKT) cells was detected by flow cytometry. The serum level of sol-CXCL6 was determined by ELISA.

RESULTS

Compared with controls, patients with metabolic syndrome showed significantly increased waist circumference and levels of total cholesterol, triglycerides and low-density lipoprotein cholesterol (all P < 0.001), with increased abnormalities of the structure and function of the carotid artery (P < 0.05). In metabolic syndrome, the levels of sol-CXCL16 and CXCL16mRNA were increased and associated with max IMT and plaque index. Patients with metabolic syndrome showed increased number of CXCR6+ T cells and CXCR6+ NKT cells, which was associated with max IMT and plaque index.

CONCLUSIONS

CXCL16 and CXCR6 may be associated the formation of carotid atherosclerotic plaque in metabolic syndrome, and T cells may be the important effector cells in the pathogenesis of the atherosclerosis.

Peripheral CD300a+CD8+ T lymphocytes with a distinct cytotoxic molecular signature increase in pregnant women with chronic chorioamnionitis

PROBLEM

  CD300a is an immunomodulatory molecule of the immunoglobulin receptor superfamily expressed in the leukocytes of myeloid and lymphoid lineages. However, its biological function on CD8+ T lymphocytes remains largely unknown. This study was conducted to assess the biological significance of CD300a expression in T lymphocytes and to determine whether its expression in peripheral T lymphocytes changes in pregnant women presenting with antifetal rejection.

METHODS OF STUDY

Microarray analysis was performed using total RNA isolated from peripheral CD300a+ and CD300a- T lymphocytes. Flow cytometric analysis of the peripheral blood samples of pregnant women and pathologic examination of the placentas were conducted.

RESULTS

  A large number of genes (N = 1245) were differentially expressed between CD300a- and CD300a+ subsets of CD8+ T lymphocytes, which included CCR7, CD244, CX3CR1, GLNY, GZMB, GZMK, IL15, ITGB1, KLRG1, PRF1, and SLAMF7. Gene ontology analysis of differentially expressed genes demonstrated enrichment of biological processes such as immune response, cell death, and signal transduction. CD300a expression in CD8+ T lymphocytes was coupled to a more cytotoxic molecular signature. Of note, the proportion of CD300a+CD8+ T lymphocytes increased in pregnant women with chronic chorioamnionitis (antifetal rejection of the chorioamniotic membranes; P < 0.05).

CONCLUSION

  The findings of this study strongly suggest an increase in systemic T-lymphocyte-mediated cytotoxicity in pregnant women with chronic chorioamnionitis as a manifestation of maternal antifetal rejection.

TWEAK (tumor necrosis factor-like weak inducer of apoptosis) activates CXCL16 expression during renal tubulointerstitial inflammation

TWEAK (tumor necrosis factor-like weak inducer of apoptosis) is a TNF superfamily cytokine that activates the fibroblast growth factor-inducible 14 (Fn14) receptor. Transcriptional analysis of experimental kidney tubulointerstitial inflammation showed a correlation between an upregulation of the mRNA for the transmembrane chemokine CXCL16, a T-cell chemoattractant, and Fn14 activation. Exogenous TWEAK increased mouse kidney CXCL16 expression and T-lymphocyte infiltration in vivo, processes inhibited by the NF-κB inhibitor parthenolide. Tubular cell CXCL16 was increased in a nephrotoxic tubulointerstitial inflammation model and neutralizing anti-TWEAK antibodies decreased this CXCL16 expression and lymphocyte infiltration. In human kidney biopsies with tubulointerstitial inflammation, tubular cell CXCL16 and Fn14 expressions were associated with inflammatory infiltrates. TWEAK upregulated CXCL16 mRNA expression in cultured renal tubular cells in an NF-κB-dependent manner and increased soluble and cellular CXCL16 protein. CXCL16 modestly promoted the expression of cytokines in tubular cells expressing its receptor (CXCR6) and appeared to synergize with TWEAK to promote an inflammatory response; however, it did not modulate tubular cell proliferation or survival. Thus, TWEAK upregulates the expression of the chemokine CXCL16 in tubular epithelium and this may contribute to kidney tubulointerstitial inflammation.

Oxidized low-density lipoprotein and tissue factor are involved in monocrotaline/lipopolysaccharide-induced hepatotoxicity

These studies were aimed at characterizing an animal model of inflammation-induced hepatotoxicity that would mimic features of idiosyncratic liver toxicity observed in humans. An attempt was made to identify oxidative damage and the involvement of coagulation system in liver after monocrotaline (MCT) administration under the modest inflammatory condition induced by lipopolysaccharide (LPS) exposure. Mice were given MCT (200 mg/kg) or an equivalent volume of sterile saline (Veh.) po followed 4 h later by ip injection of LPS (6 mg/kg) or vehicle. Mice co-treated with MCT and LPS showed increased plasma alanine aminotransferase (ALT), decrease in platelet number, and a reduction in hematocrit. Accumulation of oxidized low-density lipoprotein (ox-LDL) was remarkably higher in the liver sections of mice co-treated with MCT and LPS compared to those given MCT or LPS alone. A similar trend was observed in the expression of CXCL16 receptor in the same liver sections. Elevated expression of tissue factor (TF) and fibrinogen was also observed in the liver sections of MCT/LPS co-treated mice. The in vitro results showed that incubation of HepG2 cells with CXCL16 antibody strongly diminished uptake of ox-LDL. Expression of ox-LDL, CXCL16, and TF represents an early event in the onset of hepatotoxicity induced by MCT/LPS; thus, it may contribute to our understanding of idiosyncratic liver injury and points to potential targets for protection or intervention.

Overexpression of CXCL16 promotes a vulnerable plaque phenotype in Apolipoprotein E-Knockout Mice

BACKGROUND

CXCL16 has been shown to be involved in atherosclerotic lesion development, but its role in preexisting lesions is still unclear. This study aims to assess the effect of CXCL16 on the stability of preexisting lesions.

METHODS

We firstly measured plasma CXCL16 level in Apolipoprotein E-Knockout (ApoE KO) mice with either high-cholesterol diet (HCD) or normal diet (ND) by enzyme-linked immunosorbent assay (ELISA). Then, silastic collars were placed around the carotid arteries in HCD-ApoE KO mice to accelerate atherosclerotic lesions. Five weeks later, CXCL16 was overexpressed by intravenous injection of lentivirus carrying CXCL16 transgene. Two weeks after infection, lesions were stained with hematoxylin and eosin (HE) and with oil red O. Biomarkers in the lesions, such as MMPs, CCL2, VCAM-1 and TNF-α were measured by real-time polymerase chain reaction (RT-PCR), which indicate the instability of plaques.

RESULTS

The level of CXCL16 in plasma was higher in HCD-ApoE KO mice as compared to ND-ApoE KO mice. Circulating CXCL16 overexpression does not affect the size of preexisting plaques, but it leads to vulnerable plaque morphology and increases the expression of markers of plaque destabilization.

CONCLUSION

Systemic CXCL16 becomes much higher in atherosclerosis, and it could be a potential atherogenic biomarker. Overexpression of CXCL16 promotes the evolution of preexisting lesions to vulnerable plaques in ApoE KO mice.

Cxcl16 interact with SARS-CoV N protein in and out cell

Our study investigated the host cell protein which can interact with SARS-CoV N protein, and explored the functional connections. The eukaryotic expression vectors pEGFP-N1/SARS-CoVN and pdsRed2-N1/CXCL16 were constructed and used to co-transfect HEK293FT cells by the calcium phosphate method. The HIS-tagged fusion protein SARS-CoVN-GFP was then built and purified for the binding assay in vitro. The co-localization of SARS-CoVN and CXCL16 in the cytoplasm of HEK293FT cells was also shown using confocal laser scanning microscopy. It is suggested that their interaction might be through direct combination. Under a fluorescence microscope, it was observed that the purified fusion protein SARS-CoVN-GFP was attached to the cell membrane of CXCL16-transfected cells, indicating that SARS-CoVN and CXCL16 can be mutually combined.

Scavenger receptors and their potential as therapeutic targets in the treatment of cardiovascular disease

Scavenger receptors act as membrane-bound and soluble proteins that bind to macromolecular complexes and pathogens. This diverse supergroup of proteins mediates binding to modified lipoprotein particles which regulate the initiation and progression of atherosclerotic plaques. In vascular tissues, scavenger receptors are implicated in regulating intracellular signaling, lipid accumulation, foam cell development, and cellular apoptosis or necrosis linked to the pathophysiology of atherosclerosis. One approach is using gene therapy to modulate scavenger receptor function in atherosclerosis. Ectopic expression of membrane-bound scavenger receptors using viral vectors can modify lipid profiles and reduce the incidence of atherosclerosis. Alternatively, expression of soluble scavenger receptors can also block plaque initiation and progression. Inhibition of scavenger receptor expression using a combined gene therapy and RNA interference strategy also holds promise for long-term therapy. Here we review our current understanding of the gene delivery by viral vectors to cells and tissues in gene therapy strategies and its application to the modulation of scavenger receptor function in atherosclerosis.

Serum CXCL16 Concentrations Correlate with the Extent of Skin Sclerosis in Patients with Systemic Sclerosis

Objective.

To determine serum concentrations of soluble CXCL16 and its clinical associations in patients with systemic sclerosis (SSc).

Methods.

Serum CXCL16 levels from 89 patients with SSc were examined by ELISA. In a retrospective longitudinal study, 68 sera from 28 patients with SSc were analyzed (followup 1.3 to 7.3 yrs).

Results.

Serum CXCL16 levels were elevated in patients with SSc compared with healthy controls (n = 42). Patients with diffuse cutaneous SSc (n = 52) had higher levels of CXCL16 than those with limited cutaneous SSc (n = 37). Serum CXCL16 levels correlated positively with the extent of skin sclerosis. In the longitudinal study, CXCL16 levels generally decreased on a parallel with the improvement in skin sclerosis.

Conclusion.

CXCL16 levels were increased in patients with SSc, and correlated with the extent of skin sclerosis, suggesting that CXCL16 may have a role in the development of skin fibrosis in SSc. Blockade of CXCL16 interaction might be a potential therapeutic target in patients with SSc.

Human gingival fibroblasts express functional chemokine receptor CXCR6

We have reported that CXCL16, a recently discovered transmembrane chemokine, is expressed in human gingival fibroblasts (HGF). However, it is not known whether HGF express CXCR6, the receptor for CXCL16, or CXCL16 affects HGF biology. We have shown that HGF expressed CXCR6 by reverse transcription-polymerase chain reaction and flow cytometric analysis. Moreover, we elucidated that tumour necrosis factor (TNF)-alpha and cytosine-guanine dinucleotide (CpG) DNA (Toll-like receptor-9 ligand) treatment enhanced CXCR6 expression by HGF. Interleukin (IL)-4, IL-13 and CpG DNA up-regulated CXCR6 expression by TNF-alpha-stimulated HGF. On the other hand, IL-1beta and interferon-gamma inhibited CXCR6 expression on TNF-alpha-treated HGF. CXCL16 treatment induced HGF proliferation and phosphorylation of extracellular regulated kinase (ERK) and protein kinase B (AKT) in HGF. In conclusion, HGF expressed CXCR6 functionally, because CXCL16 induced HGF proliferation and ERK and AKT phosphorylation in HGF. These results indicate that CXCL16 may play an important role in the pathogenesis and remodelling in periodontally diseased tissues.

CXCL16 is expressed in podocytes and acts as a scavenger receptor for oxidized low-density lipoprotein

Podocytes are a crucial cell type in the kidney and play an important role in the pathology of glomerular kidney diseases like membranous nephropathy (MN). The identification of new factors involved in the progression of glomerular kidney diseases is of great importance to the development of new strategies for the treatment of renal injury. Here we demonstrate that CXCL16 and ADAM10 are constitutively expressed in human podocytes in normal renal tissue. Proinflammatory cytokines like interferon-gamma and tumor necrosis factor-alpha induced the expression of cellular CXCL16 and the release of its soluble form from human podocytes. Using different metalloproteinase inhibitors, we provide evidence that ADAM10 is involved in the interferon-gamma- and tumor necrosis factor-alpha-induced shedding of CXCL16 from human podocytes. In addition, ADAM10 knockdown by siRNA significantly increased both CXCL16 levels and, surprisingly, its ADAM17-mediated release. Notably, targeting of CXCL16 in human podocytes both decreased the chemotaxis of CXCR6-expressing T cells and strongly reduced oxidized low-density lipoprotein uptake in human podocytes. Importantly, in kidney biopsies of patients with MN, increased glomerular CXCL16 expression was accompanied by high levels of oxidized low-density lipoprotein and decreased expression of ADAM10. In addition, we found increased glomerular ADAM17 expression in patients diagnosed with MN. In summary, we presume important roles for CXCL16, ADAM10, and ADAM17 in the development of MN, suggesting these proteins as new therapeutic targets in this glomerular kidney disease.

CXCR6-CXCL16 interaction in the pathogenesis of Juvenile Idiopathic Arthritis

In order to evaluate the role of CXCR6/CXCL16 in driving lymphocyte migration into inflamed joints of children with oligoarticular Juvenile Idiopathic Arthritis (JIA) we analysed CXCR6 expression and functional capability in lymphocytes from synovial fluid (SF) by flow cytometry, by real-time polymerase chain reaction (RT-PCR) and migration assays. Furthermore, CXCR6 and CXCL16 expression in synovial tissue (ST) was analysed by immunohistochemistry. T cells isolated from SF of patients with JIA expressed CXCR6 which was functionally active as shown by chemotactic assays. The same cells expressed CXCR3 and it exerted a migratory activity in response to CXCL10. CXCL16 and CXCR6 were intensively expressed on the synovium cells, respectively on macrophages, synoviocytes and endothelial cells and on lymphocytes, synoviocytes and endothelial cells. Taken together, these data suggest that CXCR6 and CXCR3 act coordinately with respective ligands and are involved in the pathophysiology of JIA-associated inflammatory processes.

CXCL16/SR-PSOX--a friend or a foe in atherosclerosis?

Chemokines, scavenger receptors and adhesion molecules have long been known as important players in the pathogenesis of atherosclerosis. A series of studies conducted in the past few years described CXCL16/SR-PSOX--a new molecule combining those three functions, and suggested that CXCL16/SR-PSOX can be a potential player in atherogenesis. Initial ex vivo studies showed that CXCL16/SR-PSOX is abundant in human and murine atherosclerotic lesions. Following in vitro studies suggested that as an adhesion molecule CXCL16/SR-PSOX might mediate T-cell adhesion to the endothelium, as a chemokine - drive T-cell migration, stimulate cell proliferation and elicit inflammatory phenotype in smooth muscle cells (SMC) and, finally, as a scavenger receptor - mediate uptake of atherogenic lipoproteins by macrophages and SMC. All these effects are known to be pro-atherogenic. Surprisingly, in vivo studies performed in murine models of atherosclerosis suggested that CXCL16/SR-PSOX is atheroprotective, while its receptor CXCR6 is harmful. In addition, studies investigating the association of circulating CXCL16/SR-PSOX plasma concentrations with the presence and extent of coronary artery disease (CAD) in humans are controversial suggesting both positive, negative and no association. To finally answer the question whether CXCL16/SR-PSOX can serve as a causative factor, biomarker or even a therapeutic target in atherosclerosis, we are currently in need of carefully designed animal and human studies investigating the effects of CXCL16/SR-PSOX and CXCR6 deficiency, inhibition and over-expression on the progression of atherosclerosis. Such complex approach will help us unravel the mystery of CXCL16/SR-PSOX in atherosclerosis and hopefully develop better ways of treating atherosclerosis by targeting this interesting molecule.

CXCR6 promotes atherosclerosis by supporting T-cell homing, interferon-gamma production, and macrophage accumulation in the aortic wall

BACKGROUND

T lymphocytes are thought to be important in atherosclerosis, but very little is known about the mechanisms of lymphocyte recruitment into atherosclerosis-prone aortas. In this study we tested the hypothesis that CXCR6, a chemokine receptor that is expressed on a subset of CD4+ T helper 1 cells and natural killer T cells, is involved in lymphocyte homing into the aortic wall and modulates the development and progression of atherosclerosis.

METHODS AND RESULTS

To investigate the role of CXCR6 in the development and progression of atherosclerosis, we bred CXCR6-deficient (CXCR6(GFP/GFP)) mice with apolipoprotein E-deficient (ApoE(-/-)) mice. We found that CXCR6(GFP/GFP)/ApoE(-/-) mice fed a Western diet for 17 weeks or a chow diet for 56 weeks had decreased atherosclerosis compared with ApoE(-/-) controls. Flow cytometry analysis of the aortas from CXCR6(GFP/GFP)/ApoE(-/-) mice showed that the reduction of atherosclerosis was accompanied by a decreased percentage of CXCR6+ T cells within the aortas. Short-term homing experiments demonstrated that CXCR6 is involved in the recruitment of CXCR6+ leukocytes into the atherosclerosis-prone aortic wall. The reduced percentage of CXCR6+ T cells within the aortas resulted in significantly diminished production of interferon-gamma and reduction of CD11b+/CD68+ macrophages in the aorta.

CONCLUSIONS

These data provide evidence for a proatherosclerotic role of CXCR6. Absence of CXCR6 alters the recruitment of CXCR6+ leukocytes and modulates the local immune response within the aortic wall.

Inhibition of CXCL16 attenuates inflammatory and progressive phases of anti-glomerular basement membrane antibody-associated glomerulonephritis

Chemokines recruit and activate leukocytes during inflammation. CXCL16 is a recently discovered chemokine that is expressed as a transmembrane protein that is cleaved to form the active, soluble chemokine. We analyzed the role of CXCL16 in the development of inflammation and in the progression of the anti-glomerular basement membrane (GBM) antibody-induced experimental glomerulonephritis in Wistar-Kyoto rats. CXCL16 was expressed in glomerular endothelial cells and mediated adhesion of macrophages expressing CXCL16 and its cognate receptor, CXCR6. Glomerular infiltrates displayed a strong migratory response to soluble CXCL16. Soluble CXCL16 and its receptor CXCR6 were induced in nephritic glomeruli throughout the disease, and CXCL16 expression correlated with the up-regulation of ADAM10, suggesting that this disintegrin and metalloproteinase mediates the chemokine activity of CXCL16. Blocking CXCL16 in the acute inflammatory phase or progressive phase of established glomerulonephritis significantly attenuated monocyte/macrophage infiltration and glomerular injury; proteinuria also improved. We conclude that CXCL16/CXCR6 plays a critical role in stimulating leukocyte influx, which causes glomerular damage during anti-GBM glomerulonephritis. Blocking CXCL16 actions limits the progression of anti-GBM glomerulonephritis even when the disease is established.

CXC chemokine ligand 16 in periodontal diseases: expression in diseased tissues and production by cytokine-stimulated human gingival fibroblasts

Periodontal disease is an inflammatory disorder characterized by the involvement of chemokines that are important for the recruitment of leucocytes. Several cytokines are involved in regulating levels of chemokines in periodontal disease. CXCL16 is a chemokine related to the migration of T helper 1 (Th1) cells and natural killer (NK) cells. In this study, we examined its expression in periodontal tissues. Moreover, we investigated the effects of cytokines on the production of CXCL16 by human gingival fibroblast (HGF). Reverse transcription-polymerase chain reaction (RT-PCR) analysis and immunohistochemistry revealed that CXCL16 and its receptor, CXCR6, were expressed at the mRNA and protein levels in diseased tissues. Proinflammatory cytokines [interleukin (IL)-1beta, tumour necrosis factor (TNF)-alpha and interferon (IFN)-gamma] increased the mRNA expression and release of CXCL16 in a dose-dependent manner. Moreover, treatment of HGFs with IFN-gamma in combination with IL-1beta had a synergistic effect on the production of CXCL16. On the other hand, IL-4 and IL-13 inhibited the IL-1beta-induced CXCL16 production by HGFs. Inhibitors of A disintegrin and metalloprotease (ADAM)10 and ADAM17, a recently identified protease of CXCL16, reduced the amount of CXCL16 released from HGFs. These results suggest that the CXCL16 produced by HGFs may be involved in the migration of leucocytes into inflamed tissues, and provide evidence that CXCL16 production is controlled by cytokines in periodontal disease.

Anti-tumor necrosis factor-alpha antibody treatment reduces serum CXCL16 levels in patients with rheumatoid arthritis

The aim of this study was to analyze the change of serum chemokins levels of CXCL16, CX3CL1/Fractalkine, and CXCL10/interferon-gamma inducible protein-10 (IP-10) with rheumatoid arthritis (RA), by infliximab treatment. The effects of infliximab treatment were studied in 23 patients with RA, over a period of 30 weeks. The serum levels of CXCL16, Fractalkine, and IP-10, were measured at the baseline, just before initial treatment, and at 14 and 30 weeks after the initial treatment, with infliximab by ELISA. The higher levels of serum CXCL16 in the RA patients before treatment with infliximab significantly decreased at 14 and 30 weeks after the initial treatment with infliximab, but the serum Fractalkine and IP-10 levels did not decrease significantly. Infliximab treatment significantly lowered the serum levels of CXCL16 in patients with RA. CXCL16 is one of the crucial chemokines regulated by infliximab treatment.

CXCL16-mediated cell recruitment to rheumatoid arthritis synovial tissue and murine lymph nodes is dependent upon the MAPK pathway

OBJECTIVE

Rheumatoid arthritis (RA) is characterized by profound mononuclear cell (MNC) recruitment into synovial tissue (ST), thought to be due in part to tumor necrosis factor alpha (TNFalpha), a therapeutic target for RA. Although chemokines may also be involved, the mechanisms remain unclear. We undertook this study to examine the participation of CXCL16, a novel chemokine, in recruitment of MNCs to RA ST in vivo and to determine the signal transduction pathways mediating this process.

METHODS

Using a human RA ST-SCID mouse chimera, immunohistochemistry, enzyme-linked immunosorbent assay, real-time reverse transcription-polymerase chain reaction, flow cytometry, and in vitro chemotaxis assays, we defined the expression and function of CXCL16 and its receptor, CXCR6, as well as the signal transduction pathways utilized by them for MNC homing in vitro and in vivo.

RESULTS

CXCL16 was markedly elevated in RA synovial fluid (SF) samples, being as high as 145 ng/ml. Intense macrophage and lining cell staining for CXCL16 in RA ST correlated with increased CXCL16 messenger RNA levels in RA ST compared with those in osteoarthritis and normal ST. By fluorescence-activated cell sorting analysis, one-half of RA SF monocytes and one-third of memory lymphocytes expressed CXCR6. In vivo recruitment of human MNCs to RA ST implanted in SCID mice occurred in response to intragraft injection of human CXCL16, a response similar to that induced by TNFalpha. Lipofection of MNCs with antisense oligodeoxynucleotides for ERK-1/2 resulted in a 50% decline in recruitment to engrafted RA ST and a 5-fold decline in recruitment to regional lymph nodes. Interestingly, RA ST fibroblasts did not produce CXCL16 in response to TNFalpha in vitro, suggesting that CXCL16 protein may function in large part independently of TNFalpha.

CONCLUSION

Taken together, these results point to a unique role for CXCL16 as a premier MNC recruiter in RA and suggest additional therapeutic possibilities, targeting CXCL16, its receptor, or its signaling pathways.

Pathogenic role of the CXCL16-CXCR6 pathway in rheumatoid arthritis

OBJECTIVE

Rheumatoid arthritis (RA) is a chronic inflammatory disease associated with massive T cell infiltration into the synovium. The accumulated T cells express type 1 cytokines, such as interferon-gamma (IFNgamma) and tumor necrosis factor alpha, and activated markers of inflammation, such as CD154 and inducible costimulator (ICOS). It is thought that chemokines contribute to T cell accumulation in the synovium. In this study, we examined the role of CXCL16 and CXCR6 in T cell migration and stimulation in RA synovium.

METHODS

Expression of CXCL16 and CXCR6 was analyzed by immunohistochemistry, reverse transcription-polymerase chain reaction, Western blotting, and/or flow cytometry. Migration activity was assessed using a chemotaxis chamber. IFNgamma production was analyzed by enzyme-linked immunosorbent assay. The effect of anti-CXCL16 monoclonal antibody on murine collagen-induced arthritis (CIA) was evaluated.

RESULTS

CXCL16 was expressed in RA synovium. CXCR6 was expressed more frequently on synovial T cells than in peripheral blood. Moreover, CXCR6-positive synovial T cells more frequently expressed CD154 and ICOS than did CXCR6-negative T cells. Stimulation with interleukin-15 (IL-15) up-regulated the expression of CXCR6 on peripheral blood T cells, and then stimulation with CXCL16 induced migration of IL-15-stimulated T cells and enhanced IFNgamma production. Furthermore, anti-CXCL16 monoclonal antibody significantly reduced the clinical arthritis score and reduced infiltration of inflammatory cells and bone destruction in the synovium of mice with CIA.

CONCLUSION

Our results indicate that CXCL16 plays an important role in T cell accumulation and stimulation in RA synovium and suggest that CXCL16 could be a target molecule in new therapies for RA.

The pro-atherogenic cytokine interleukin-18 induces CXCL16 expression in rat aortic smooth muscle cells via MyD88, interleukin-1 receptor-associated kinase, tumor necrosis factor receptor-associated factor 6, c-Src, phosphatidylinositol 3-kinase, Akt, c-Jun N-terminal kinase, and activator protein-1 signaling

We recently demonstrated that the chemokine CXCL16 is expressed in aortic smooth muscle cells (ASMC) and induces ASMC adhesion and proliferation (Chandrasekar, B., Bysani, S., and Mummidi, S. (2004) J. Biol. Chem. 279, 3188-3196). Here we reort that interleukin (IL)-18 positively regulates CXCL16 transcription in rat ASMC. We characterized the cis-regulatory region of CXCL16 and identified a functional activator protein-1 (AP-1) binding motif. Deletion or mutation of this site attenuated IL-18-mediated CXCL16 promoter activity. Gel shift, supershift, and chromatin immunoprecipitation assays confirmed AP-1-dependent CXCL16 expression. CXCL16 promoter-reporter activity was increased by constitutively active c-Fos and c-Jun and decreased by dominant negative or antisense c-Fos and c-Jun. Src kinase inhibitors PP1 and PP2, phosphatidylinositol 3-kinase (PI3K) inhibitors wortmannin and LY294002, Akt inhibitor, the c-Jun N-terminal kinase (JNK) inhibitor SP600125, antisense JNK and dominant negative MyD88, interleukin-1 receptor-associated kinase (IRAK)-1, IRAK4, and phosphatidylinositol 3-kinase expression all attenuated IL-18-mediated AP-1 binding and reporter activity, CXCL16 promoter-reporter activity, and CXCL16 expression. Thus IL-18 induced CXCL16 expression via a MyD88 --> IRAK1-IRAK4-TRAF6 (tumor necrosis factor receptor-associated factor 6) --> c-Src--> PI3K --> Akt --> JNK --> AP-1 pathway. Importantly, IL-18 stimulated ASMC proliferation in a CXCL16-dependent manner. These data provide for the first time a mechanism of IL-18-mediated CXCL16 gene transcription and CXCL16-dependent ASMC proliferation and suggest a role for IL-18-CXCL16 cross-talk in atherogenesis and restenosis following angioplasty.

CXCL16 signals via Gi, phosphatidylinositol 3-kinase, Akt, I kappa B kinase, and nuclear factor-kappa B and induces cell-cell adhesion and aortic smooth muscle cell proliferation

CXCL16, a recently discovered transmembrane chemokine, is expressed in human aortic smooth muscle cell (ASMC). It facilitates uptake of low density lipoproteins by macrophages, resulting in foam cell formation. However, it is not known whether ASMC express CXCR6, the receptor for CXCL16, or whether CXCL16 affects ASMC biology. To dissect the biological and signal transduction pathways elicited by CXCL16, human aortic smooth muscle cells (HASMC) were treated with pharmacological inhibitors or transiently transfected with pathway-specific dominant-negative or kinase-dead expression vectors prior to the addition of CXCL16. HASMC expressed CXCR6 at basal conditions. Exposure of HASMC to CXCL16 increased NF-kappa B DNA binding activity, induced kappa B-driven luciferase activity, and up-regulated tumor necrosis factor-alpha expression in an NF-kappa B-dependent manner. However, treatment with pertussis toxin (G(i) inhibitor), wortmannin or LY294002 (phosphatidylinositol 3-kinase (PI3K inhibitors)), or Akt inhibitor or overexpression of dominant-negative (dn) PI3K gamma, dnPDK-1, kinase-dead (kd) Akt, kdIKK-beta, dnIKK-gamma, dnI kappa B-alpha, or dnI kappa B-beta significantly attenuated CXCL16-induced NF-kappa B activation. Furthermore, CXCL16 increased cell-cell adhesion and induced cellular proliferation in an NF-kappa B-dependent manner. In conclusion, CXCL16 is a potent and direct activator of NF-kappaB and induces kappa B-dependent proinflammatory gene transcription. CXCL16-mediated NF-kappa B activation occurred via heterotrimeric G proteins, PI3K, PDK-1, Akt, and I kappa B kinase (IKK). CXCL16 induced I kappa B phosphorylation and degradation. Most importantly, CXCL16 increased cell-cell adhesion and induced kappa B-dependent ASMC proliferation, indicating that CXCL16 may play an important role in the development and progression of atherosclerotic vascular disease.