Donate Help Contact The AHA Sign In Home
American Heart Association
Arteriosclerosis, Thrombosis, and Vascular Biology
Search: search_blue_button Advanced Search
Arteriosclerosis, Thrombosis, and Vascular Biology. 2004;24:282-287
Published online before print December 29, 2003, doi: 10.1161/01.ATV.0000114565.42679.c6
This Article
Right arrow Abstract Freely available
Right arrow Full Text (PDF)
Right arrow Data Supplement
Right arrow All Versions of this Article:
24/2/282    most recent
01.ATV.0000114565.42679.c6v1
Right arrow Submit a response
Right arrow Alert me when this article is cited
Right arrow Alert me when eLetters are posted
Right arrow Alert me if a correction is posted
Right arrow Citation Map
Services
Right arrow Email this article to a friend
Right arrow Similar articles in this journal
Right arrow Similar articles in PubMed
Right arrow Alert me to new issues of the journal
Right arrow Download to citation manager
Right arrowRequest Permissions
Citing Articles
Right arrow Citing Articles via HighWire
Right arrow Citing Articles via Google Scholar
Google Scholar
Right arrow Articles by Yamauchi, R.
Right arrow Articles by Kita, T.
Right arrow Search for Related Content
PubMed
Right arrow PubMed Citation
Right arrow Articles by Yamauchi, R.
Right arrow Articles by Kita, T.
Right arrowPubmed/NCBI databases
*Gene*GEO Profiles
*HomoloGene*Protein
*UniGene
*Substance via MeSH
Medline Plus Health Information
*Heart Valve Diseases
*Joint Disorders
Related Collections
Right arrow Infectious endocarditis
Right arrow Growth factors/cytokines
Right arrow Valvular heart disease
Right arrow Endothelium/vascular type/nitric oxide
(Arteriosclerosis, Thrombosis, and Vascular Biology. 2004;24:282.)
© 2004 American Heart Association, Inc.


Vascular Biology

Upregulation of SR-PSOX/CXCL16 and Recruitment of CD8+ T Cells in Cardiac Valves During Inflammatory Valvular Heart Disease

Ryoko Yamauchi; Makoto Tanaka; Noriaki Kume; Manabu Minami; Takahiro Kawamoto; Kiyonori Togi; Takeshi Shimaoka; Shu Takahashi; Junko Yamaguchi; Takeshi Nishina; Masanori Kitaichi; Masashi Komeda; Toshiaki Manabe; Shin Yonehara; Toru Kita

From the Department of Cardiovascular Medicine (R.Y., N.K., T.K.), Graduate School of Medicine, Kyoto University, Kyoto, Japan; the Department of Social Service (M.T.), Kyoto University Hospital, Kyoto, Japan; the Department of Geriatric Medicine (M.T., M.M., T.K., K.T.), Graduate School of Medicine, Kyoto University, Kyoto, Japan; the Institute for Viral Research (T.S., S.Y.), Kyoto University, Kyoto, Japan; Biomedical Research Laboratories (S.T., J.Y.), Sankyo Co., Ltd, Tokyo, Japan; the Department of Cardiovascular Surgery (T.N., M.K.), Graduate School of Medicine, Kyoto University, Kyoto, Japan; and the Department of Anatomic Pathology (M.K., T.M.), Kyoto University Hospital, Kyoto, Japan.

Correspondence to Dr Makoto Tanaka, Department of Social Service, Kyoto University Hospital, 54 Shogoin-Kawahara-cho, Sakyo-ku, Kyoto 606-8507, Japan. E-mail makoto{at}kuhp.kyoto-u.ac.jp


*    Abstract
up arrowTop
*Abstract
down arrowIntroduction
down arrowMethods
down arrowResults
down arrowDiscussion
down arrowReferences
 
Objective— SR-PSOX/CXCL16 is a transmembrane chemokine and is implicated in activated CD8+ T cell trafficking. In the present study, we examined the expression pattern of SR-PSOX/CXCL16 in the heart and investigated a potential role of SR-PSOX/CXCL16 in inflammatory valvular heart disease.

Methods and Results— Initial expression of SR-PSOX/CXCL16 in murine embryos was detected in endothelial cells lining endocardial cushions in the forming heart at E11.5. From mid-gestation to adult, expression of this gene in the heart was exclusively observed in valvular endothelial cells. Examination of SR-PSOX/CXCL16 expression in human cardiac valves demonstrated that SR-PSOX/CXCL16 was strongly expressed in valvular and neocapillary endothelial cells in patients with infective endocarditis. SR-PSOX/CXCL16 expression in neocapillary endothelial cells was also observed in patients with rheumatic and atherosclerotic valvular disease. Moreover, CD8+ T cells were distributed closely to endothelial cells expressing SR-PSOX/CXCL16. In vitro adhesion assays showed that SR-PSOX/CXCL16 induced adhesion of activated CD8+ T cells to vascular cell adhesion molecule-1 (VCAM-1) through very late antigen-4 (VLA-4) activation. Furthermore, SR-PSOX/CXCL16 stimulated interferon-{gamma} (IFN-{gamma}) production by CD8+ T cells.

Conclusions— SR-PSOX/CXCL16 may be involved in CD8+ T cell recruitment through VLA-4 activation and stimulation of IFN-{gamma} production by CD8+ T cells during inflammatory valvular heart disease.


Key Words: SR-PSOX/CXCL16 • cardiac valve • endothelial cell • infective endocarditis • CD8+ T cell


*    Introduction
up arrowTop
up arrowAbstract
*Introduction
down arrowMethods
down arrowResults
down arrowDiscussion
down arrowReferences
 
Chemokines are a group of small, structurally related proteins with four conserved cysteines forming two essential disulphide bonds. Based on NH2-terminal cysteine motifs, chemokines are classified into four major subfamilies: CC, CXC, C, and CX3C.1,2 Although increasing evidence has demonstrated multiple functions of chemokines, including lymphocyte differentiation3 and angiogenesis,4,5 the main function of chemokines is lymphocyte traffic control.6 7 Chemokine gradients mediate chemotaxis by providing directional cues for lymphocyte motility.7,8 Chemokines also play a key role in lymphocyte/endothelial-cell recognition. Chemokines presented on endothelial cells trigger rapid activation of integrins, resulting in arrest and firm adhesion of lymphocytes.7,9,10

Based on functional characteristics, chemokines are classified into homeostatic and inflammatory chemokines. Homeostatic chemokines are produced constitutively and are involved in the proper development and homeostasis of the immune system.7,11 Inflammatory chemokines are upregulated under inflammatory conditions and recruit effector cells, including monocytes, granulocytes, and effector T cells, through integrin activation.7,11

SR-PSOX/CXCL16 is a CXC chemokine and exists in a transmembrane form.12–14 SR-PSOX/CXCL16 is expressed in dendritic cells in lymphoid organs and attracted activated T cells in vitro, suggesting that it may be involved in T cell-antigen presenting cell interactions in initiation of immune responses.12,14 Moreover, upregulation of SR-PSOX/CXCL16 by inflammatory stimuli indicated that SR-PSOX/CXCL16 may be involved in efficient recruitment of effector T cells into inflammatory lesions.12 Although the expression of SR-PSOX/CXCL16 has been described in adult lymphoid tissues,12 its distribution pattern outside the immune system is unknown. Therefore, in this study, we first examined the spatial and temporal expression pattern of SR-PSOX/CXCL16 during murine development. Interestingly, we found that SR-PSOX/CXCL16 was specifically expressed in endothelial cells of the cardiac valves. Histological examination of human cardiac valves and in vitro studies demonstrated that the chemokine might play an important role in CD8+ T cell recruitment and interferon-{gamma} (IFN-{gamma}) production during inflammatory valvular heart disease.


*    Methods
up arrowTop
up arrowAbstract
up arrowIntroduction
*Methods
down arrowResults
down arrowDiscussion
down arrowReferences
 
Mouse Tissue Samples, In Situ Hybridization, and Immunohistochemistry
Noon on the day of mating was referred to as E0.5 (day 0.5 postcoitus). Paraffin sections (5 µm) of embryonic and adult tissues from C57BL/6 mice were fixed with 4% paraformaldehyde, treated with 0.1 mol/L HCl, acetylated in 0.25% acetic anhydride in 0.1 mol/L triethanolamine, and hybridized with 35S-CTP–labeled riboprobe at 55°C overnight in 50% formamide, 0.3 mol/L sodium chloride, 20 mmol/L Tris-HCl, 5 mmol/L EDTA, 10 mmol/L sodium pyrophosphate, 1XDenhardt, 10% dextran sulfate, and 0.5 mg/mL yeast RNA. After hybridization, they were treated with RNase-A, washed and dehydrated through graded ethanol, and emulsion autoradiography was performed. The SR-PSOX/CXCL16 riboprobe comprised a full-length cDNA. Hybridization with a sense probe did not give any signals.

For immunohistochemistry, paraffin sections were deparaffinized in xylene and rehydrated in graded alcohol and incubated with anti-mouse CXCL16 antibody (R&D Systems, Minneapolis, MN) or anti-mouse platelet–endothelial cell adhesion molecule-1 (PECAM-1) antibody (Pharmingen, San Diego, CA) overnight at 4°C. After washing, sections were incubated with biotinylated goat anti-mouse IgG and horseradish peroxidase-conjugated streptavidin (Vector Laboratories, Burlingame, CA), and staining was detected with 3,3'-diaminobenzidine (DAB).

Human Tissue Samples and Immunohistochemistry
Paraffin sections (5 µm) were prepared from human valve specimens from 14 patients who underwent valve replacement. The diagnosis of rheumatic valve disease was based on a history of rheumatic fever and characteristic echocardiographic features. All tissue samples were fixed in 10% neutral formalin and embedded in paraffin wax. Sections were deparaffinized in xylene, rehydrated in graded alcohol, and autoclaved for 10 minutes at 121°C in 10 nM EDTA (pH 8.0). The tissue sections were then incubated with anti-SR-PSOX/CXCL16, anti-CD8, anti-CD4, anti-CD68, anti-CD29, or anti-VCAM-1 antibody overnight at 4°C. Anti-human SR-PSOX/CXCL16 monoclonal antibody was generated by immunizing mice with recombinant human SR-PSOX/CXCL16 protein. The antibody gave a single band on Western blotting (R.Y. and M.T., unpublished data) and inhibited chemotactic activity of human SR-PSOX/CXCL16 on human CXCR6-expressiong cells.15 Monoclonal anti-human CD8+ and CD4+ antibodies were purchased from Medical & Biological Laboratories (Nagoya, Japan), and monoclonal anti-human CD29, CD34, and VCAM-1 antibodies were from Novocastra Laboratories (Newcastle, UK). After washing, sections were incubated with biotinylated goat anti-mouse IgG and horseradish peroxidase-conjugated streptavidin, and staining was detected with DAB.

Preparation of Cell Suspension From Spleen
Lymphocytes from spleen were prepared as previously described.16,17 CD8+ T cells were prepared from spleen of C57BL/6 mice by positive selection using MACS immunobeads (Miltenyi Biotec, Bergisch Gladbach, Germany). For in vitro activation, CD8+ T cells were incubated with anti-CD28 (10 µg/mL; Pharmingen, San Diego, CA) in RPMI1640 medium supplemented with 10% fetal calf serum, 24 mmol/L NaHCO3, 50 µmol/L 2-mercaptoethanol, and IL-2 (4 ng/mL) in 96-well plates coated with anti-CD3 (1 µg/mL; Becton Dickinson, San Jose, CA) for 5 days. The activated T cells were then rested in the aforementioned medium supplemented with 2 ng/mL of IL-2 for 4 days. Recombinant human IL-2 was kindly provided by Takeda Pharmaceutical Company (Osaka, Japan).

Cell Adhesion Assay
Adhesion assay was performed as described.18–20 Briefly, polystyrene 96-well microtiter plates were coated with soluble VCAM-1 (2.5 µg/mL) and blocked by heat-denatured BSA. Activated CD8+ T cells suspended at a concentration of 1.5 x 106 /mL in 0.1% BSA-RPMI were incubated for the indicated times in a CO2 incubator at 37°C in the presence or absence of soluble SR-PSOX/CXCL16 (R&D Systems, Minneapolis, MN). After incubation, nonadherent cells were removed by centrifugation (topside down) at 48g for 5 minutes. Attached cells were fixed with 5% glutaraldehyde, stained with 0.1% crystal violet in 200 nM MES (pH 6.0), and solubilized with 10% acetic acid. The absorbance of each well at 595 nm was measured using a multiscan enzyme-linked immunosolvent assay reader (TECAN, Männedorf, Switzerland). Anti-mouse {alpha}4-integrin antibody was purchased from Pharmingen.

Cell Stimulation and Measurement of IFN-{gamma} Production
CHO cell lines stably expressing mouse SR-PSOX/CXCL16 were established by transfection with a plasmid (pME18S) expressing full-length mouse SR-PSOX/CXCL16 cDNA. After selection with 800 µg/mL of G418 for 2 weeks, drug-resistant clones were isolated, and clones expressing SR-PSOX/CXCL16 were identified by Western blotting. Activated CD8+ T cells at a concentration of 1 x 105/mL were co-cultured with control CHO cells or CHO cells stably expressing SR-PSOX/CXCL16 in 0.1% BSA-RPMI for 24 hours in 96-well plates. After incubation, 100 µL of supernatants were collected and assessed for IFN-{gamma} production using an ELISA kit (Bio Source International, Camarillo, CA) according to the manufacturer’s protocol. The detectable range of the ELISA kit was 1 to 500 pg/mL and the optical density of individual wells was determined at 450 nm using a microplate reader. Anti-mouse SR-PSOX/CXCL16 monoclonal antibody was generated by immunizing mice with recombinant mouse SR-PSOX/CXCL16 protein. This antibody gave a single band on Western blotting (R.Y. and M.T., unpublished data) and blocked chemotaxis of mouse CXCR6 expressing cells to mouse SR-PSOX/CXCL16 (T.S. and S.Y., unpublished data).

Statistical Analysis
Data were analyzed by one-factor ANOVA followed by Fisher PLSD as a post hoc test. P<0.01 was considered to be statistically significant.


*    Results
up arrowTop
up arrowAbstract
up arrowIntroduction
up arrowMethods
*Results
down arrowDiscussion
down arrowReferences
 
SR-PSOX/CXCL16 Is Expressed in Cushion and Valve Endothelium During Development
Initial expression of SR-PSOX/CXCL16 was detected in the heart at E11.5. SR-PSOX/CXCL16 mRNA was exclusively expressed in endothelial cells covering endocardial cushions (Figure 1 A through 1D). Mesenchymal cells transformed from these cushion endothelial cells lost SR-PSOX/CXCL16 expression (Figure 1A through 1D). From mid-gestation to adult, SR-PSOX/CXCL16 expression was confined to endothelial cells of the cardiac valves at mRNA (Figure 1E through 1H) and protein (Figure 1I) levels. Expression of SR-PSOX/CXCL16 protein in valvular endothelium was confirmed by positive PECAM-1 staining (Figure 1J).



View larger version (64K):
[in this window]
[in a new window]
 
Figure 1. Expression of SR-PSOX/CXCL16 in the heart is confined to valvular endothelium. In situ hybridization and immunohistochemistry of murine samples. In situ hybridization was performed on paraffin sections of mouse embryonic and adult tissues using 35S-labeled mouse SR-PSOX/CXCL16 riboprobe. A–D, Sagittal sections of day 11.5 postcoitus (A, B) and day 13.5 postcoitus (C, D) embryos. SR-PSOX/CXCL16 was expressed in endothelial cells covering the endocardial cushion (EC). RV indicates right ventricle; LV, left ventricle. E, Sagittal section of a day 13.5 postcoitus embryo, showing SR-PSOX/CXCL16 expression in the forming mitral valve (MV). AS indicates atrial septum. F, Sagittal section of a neonate, showing hybridization signals in the aortic valve (AoV). G and H, Sagittal section of an adult heart. SR-PSOX/CXCL16 was expressed in valvular endothelium. LA indicates left atrium. I and J, Immunohistochemical staining of mitral valve. SR-PSOX/CXCL16 was expressed in valvular endothelium (I), as confirmed by positive PECAM-1 staining in a serial section (J). Scales bars = 200 µm (C, F, G), 100 µm (A, D, H), 50 µm (B, E), and 10 µm (I, J)

Outside the heart, SR-PSOX/CXCL16 mRNA expression was first observed in the meninges, covering the spinal cord, dorsal root, and cerebral sulcus at E13.5. At E15.5, SR-PSOX/CXCL16 was still detected in pia mater and arachnoid. Expression of SR-PSOX/CXCL16 mRNA in lymphoid organs including the thymus and spleen was first observed at this stage. SR-PSOX/CXCL16 was also expressed in Rathke’s pouch. However, no expression of SR-PSOX/CXCL16 was detected in the adult brain. These data are shown in Figure I (available online at http://atvb.ahajournals.org).

Upregulation of SR-PSOX/CXCL16 in Inflammatory Valvular Disease
The specific expression of SR-PSOX/CXCL16 in valvular endothelium suggested that this chemokine may play a role in the pathogenesis of valvular heart disease. We thus examined expression of SR-PSOX/CXCL16 protein in human cardiac valves from patients who underwent valve replacement (Table). In noninflammatory valvular disease (prolapse of mitral valve), SR-PSOX/CXCL16 protein was undetectable (Figure 2 A). In contrast, dramatic upregulation of SR-PSOX/CXCL16 protein was observed in valvular endothelium in patients with infective endocarditis (Figure 2C, 2F, and 2H). SR-PSOX/CXCL16 protein expression in valvular endothelial cells was confirmed by positive CD34 staining (Figure 2D) and control IgG was substituted for the primary antibody in negative control experiments (Figure 2E). Macrophages (open arrowheads in Figure 2F), as revealed by positive CD68 staining (Figure 2G), also expressed SR-PSOX/CXCL16 protein. Interestingly, endothelial cells of neocapillaries within cardiac valves were also positive for SR-PSOX/CXCL16 (Figure 2J and 2M). In patients with rheumatic and atherosclerotic valvular disease, SR-PSOX/CXCL16 protein expression was observed in neocapillary endothelial cells within cardiac valves (Figure 3 C and 3E), whereas no expression was detected in valvular endothelium (Figure 3A).


View this table:
[in this window]
[in a new window]
 
Expression of CXCL 16 in Valvular and Neocapillary Endothelium



View larger version (123K):
[in this window]
[in a new window]
 
Figure 2. Upregulation of SR-PSOX/CXCL16 expression and presence of CD8+ T cells in cardiac valves in patients with infective endocarditis. Immunohistochemical staining of human cardiac valves. Paraffin sections were stained with anti-SR-PSOX/CXCL16 monoclonal antibody (A, C, F, H, J, M) or anti-CD8 monoclonal antibody (B, I, K, O). A and B, Serial sections of mitral valve from a patient with mitral valve prolapse, showing no expression of SR-PSOX/CXCL16 and absence of CD8+ T cells. C–E, Serial sections of mitral valve from a patient with infective endocarditis. SR-PSOX/CXCL16 expression was observed in valvular endothelial cells (C), as confirmed by positive CD34 staining (D). E, Control IgG did not produce any significant immunostaining. F and G, Serial sections of mitral valve from a patient with infective endocarditis. SR-PSOX/CXCL16 was expressed in valvular endothelial cells (arrowheads in F) and macrophages (open arrowheads in F), as revealed by positive CD68 staining in a serial section (G). H and I, Serial sections of aortic valve from a patient with infective endocarditis. SR-PSOX/CXCL16 expression was observed in valvular endothelial cells (H) and macrophages (open arrowheads in H). CD8+ T cells are located underneath valvular endothelial cells (I). J–L, Serial sections of mitral valve from a patient with infective endocarditis. Note SR-PSOX/CXCL16 expression in neocapillary endothelial cells (arrows in J) and CD8+ T cells infiltrate around neocapillary endothelial cells (K). There was no CD4+ T cells around neocapillary endothelial cells (L). M and N, Serial sections of mitral valve from a patient with infective endocarditis. Neocapillary endothelial cells expressing SR-PSOX/CXCL16 (M) were also positive for VCAM-1 (N). O and P, CD8+ T cell located within the neocapillary lumen (O) expressed VLA-4 (P). Scales bars = 10 µm (A–G, J–P) and 25 µm (H, I).



View larger version (182K):
[in this window]
[in a new window]
 
Figure 3. Expression of SR-PSOX/CXCL16 in neocapillary endothelial cells in patients with rheumatic and atherosclerotic valvular disease. Immunohistochemical staining of human cardiac valves. Paraffin sections were stained with anti-SR-PSOX/CXCL16 monoclonal antibody (A, C, E), or anti-CD8 monoclonal antibody (B, D, F). A–D, Serial sections of aortic valve from a patient with rheumatic valvular disease. Panels A and B show no expression of SR-PSOX/CXCL16 in valvular endothelium and absence of CD8+ T cells. However, SR-PSOX/CXCL16 expression was clearly detected in neocapillary endothelial cells (arrows in C) and close association of CD8+ T cells could be observed (D). E and F, Serial sections of aortic valve from a patient with atherosclerotic valvular disease. Neocapillary endothelial cells (arrows in E) were positive for SR-PSOX/CXCL16. CD8+ T cells were located around neocapillaries (F). Scales bars = 100 µm (A, B), 50 µm (C, D), and 10 µm (E, F).

Becauae it was previously reported that SR-PSOX/CXCL16 attracted activated CD8+ T lymphocytes in vitro, we next examined whether CD8+ T cells existed in these lesions. As expected, we detected abundant CD8+ T cells underneath valvular endothelial cells in patients with infective endocarditis (Figure 2I). CD8+ T cells were also detected around neocapillaries within cardiac valves in patients with endocarditis (Figure 2K) as well as rheumatic and atherosclerotic valvular disease (Figure 3D and 3F). No CD8+ T cells were observed in cardiac valves from patients with noninflammatory valvular disease (Figure 2B). Although SR-PSOX/CXCL16 was also shown to attract activated CD4+ T cells in vitro,12 we did not observe any CD4+ T cells in cardiac valves in patients with inflammatory valvular heart disease (Figure 2L).

SR-PSOX/CXCL16-Mediated Adhesion of Activated CD8+ T Lymphocytes to VCAM-1
The close association of SR-PSOX/CXCL16 expression with CD8+ T cells suggested that SR-PSOX/CXCL16 may be involved in CD8+ T cell recruitment. To find out if SR-PSOX/CXCL16 mediates adhesion of CD8+ T lymphocytes, we performed adhesion assays. We examined adhesion of activated CD8+ T cells to purified adhesion molecules to determine the regulation of integrin avidity by SR-PSOX/CXCL16. Interestingly, SR-PSOX/CXCL16 was able to induce firm adhesion of activated CD8+ T cells to VCAM-1 by more than 2-fold, but not to intercellular adhesion molecule-1 (ICAM-1) (Figure 4 A), whereas SR-PSOX/CXCL16 had no effects on naive CD8+ T cells (Figure 4A). Moreover, functional blocking of the {alpha}4-subunit of integrins abolished the effect of SR-PSOX/CXCL16 (Figure 4B), indicating that the adhesion mediated by SR-PSOX/CXCL16 was VLA-4–dependent.



View larger version (27K):
[in this window]
[in a new window]
 
Figure 4. SR-PSOX/CXCL16 stimulated adhesion of activated CD8+ T cells to VCAM-1 through activation of VLA-4 and enhanced IFN-{gamma} production by activated CD8+ T cells. A, Activated CD8+ T cells were subjected to adhesion assays on heat-denatured BSA (as control), ICAM-1, or VCAM-1 for 10 minutes in the presence (open columns) or absence (closed columns) of 10 nM SR-PSOX/CXCL16. Data represent the mean±SD of triplicate measurements. Results are representative of two separate experiments (*P<0.01) (left panel). Naive CD8+ T cells without activation were subjected to adhesion assays (right panel). B, Activated CD8+ T cells were preincubated with 10 µg/mL anti-{alpha}4 antibody or control IgG (cont.IgG) for 1 hour. After incubation, cells were subjected to adhesion assays on VCAM-1 in the presence of 10 nM SR-PSOX/CXCL16 for 10 minutes. Data represent the mean±SD of triplicate measurements. Results are representative of two separate experiments (*:P<0.01). C, Activated CD8+ T cells were co-cultured with either control CHO cells (CHO-) or CHO cells with stable expression of SR-PSOX/CXCL16 (CXCL16), and INF-{gamma} production was measured. For blocking experiments, activated CD8+ T cells were preincubated with anti-SR-PSOX/CXCL16–neutralizing antibody (28 µg/mL) or control IgG (cont.IgG) for 1 hour. After preincubation, activated CD8+ T cells were co-cultured with CHO cells expressing SR-PSOX/CXCL16 and IFN-{gamma} production was measured. Data represent the mean±SD of quadricate measurements. (*:P<0.01). Ab indicates antibody.

We thus examined expression of VCAM-1 and VLA-4 in cardiac valves in patients with infective endocarditis. Interestingly, neocapillary endothelial cells expressing SR-PSOX/CXCL16 were positive for VCAM-1 (Figure 2N), and CD8+ T cells within neocapillary lumens (Figure 2O) expressed VLA-4 (Figure 2P).

Stimulation of IFN-{gamma} Production in Activated CD8+ T Lymphocytes by SR-PSOX/CXCL16
To assess the involvement of SR-PSOX/CXCL16 in inflammatory processes, we examined whether SR-PSOX/CXCL16 could activate IFN-{gamma} production by CD8+ T cells. As shown in Figure 4C, co-culture with CHO cells stably expressing SR-PSOX/CXCL16 significantly enhanced IFN-{gamma} production by activated CD8+ T cells. IFN-{gamma} production by naive CD8+ T cells was undetectable either in the presence or in the absence of SR-PSCX/CXCL16 (data not shown). The enhancement of IFN-{gamma} production by SR-PSOX/CXCL16 in activated CD8+ T cells was completely blocked by anti-SR-PSOX/CXCL16 antibody (Figure 4C). Either control CHO cells or CHO cells with stable expression of SR-PSOX/CXCL16 did not produce IFN-{gamma} (data not shown).


*    Discussion
up arrowTop
up arrowAbstract
up arrowIntroduction
up arrowMethods
up arrowResults
*Discussion
down arrowReferences
 
SR-PSOX/CXCL16 was detected in the cushion endothelium at a time coincident with endothelial–mesenchymal transformation. The endothelium covering the endocardial cushion is considered to be a specific population of endothelial cells that has acquired competence to receive transformation signals from the myocardium.21 To our knowledge, SR-PSOX/CXCL16 is the first molecular marker specific for the cushion endothelium, demonstrating at a molecular level that endothelial cells covering the cushion are distinct from other endocardial cells. Furthermore, SR-PSOX/CXCL16 was later expressed in endothelial cells of the cardiac valves, indicating that valve endothelium is derived from endothelial cells covering endocardial cushions at earlier stages.

In human cardiac valves, SR-PSOX/CXCL16 expression was undetectable in the absence of valvular inflammation. The difference in the expression pattern between human and mice may be caused by species difference. Interestingly, SR-PSOX/CXCL16 expression was upregulated during inflammation and CD8+ T cells were closely associated with SR-PSOX/CXCL16-positive endothelial cells. Adhesion assays demonstrated that SR-PSOX/CXCL16 mediated adhesion of activated CD8+ T lymphocytes to VCAM-1, suggesting that SR-PSOX/CXCL16 may, at least in part, play a role in CD8+ T cell recruitment in inflammatory valvular disease. However, it is possible that other inflammatory chemokines may be also involved in this process. Lymphocyte firm adhesion generally requires activation of integrins by chemokines.7,22 The effect of SR-PSOX/CXCL16 was abolished by inhibition of the {alpha}4-integrin, indicating that SR-PSOX/CXCL16 mediates adhesion of activated CD8+ T cells to VCAM-1 through activation of VLA-4. These results were further supported by immunostaining for VCAM-1 and VLA-4.

Does SR-PSOX/CXCL16 stimulate cytokine production in activated CD8+ T cells in addition to integrin activation? Interestingly, SR-PSOX/CXCL16 enhanced IFN-{gamma} production by activated CD8+ T cells. IFN-{gamma} is an important immune-activating cytokine that mediates macrophage activation and induces inflammatory responses.23–25 In vitro studies have shown that IFN-{gamma} inhibited growth of endothelial cells and smooth muscle cells, and in vivo studies demonstrated that the proliferative response of smooth muscle cells after arterial injury was inhibited by IFN-{gamma}.26–28 Therefore, it was suggested that IFN-{gamma} may be associated with reduction of the fibrous cap, thereby destabilizing atherosclerotic plaques.24 Similarly, IFN-{gamma} production by CD8+ T cells in inflammatory valvular disease may promote remodeling and destruction of inflamed valves. Moreover, IFN-{gamma} increased expression of VCAM-1 on endothelial cells.29 The upregulation of VCAM-1 by IFN-{gamma} may further enhance CD8+ T cell trafficking mediated by SR-PSOX/CXCL16.

Expression of SR-PSOX/CXCL16 in valvular endothelium was only observed in patients with infective endocarditis. What is the pathological significance for the different expression pattern between patients with infective endocarditis and rheumatic/atherosclerotic valvular disease? First, expression of SR-PSOX/CXCL16 in valvular endothelium as well as in neocapillary endothelium may further enhance recruitment of CD8+ T cells into inflamed tissues. Second, expression of SR-PSOX/CXCL16 on valvular surface may mediate bacterial adhesion to valvular tissues. Recently, it was reported that SR-PSOX/CXCL16 mediated adhesion and phagocytosis of bacteria by antigen presenting cells.15 SR-PSOX/CXCL16 may be involved in the attachment of bacteria to valvular endothelial cells, which is the first step in the development of infective endocarditis.

Does inflammation still persist in the chronic phase of rheumatic valve disease? It was recently reported that plasma high-sensitivity C-reactive protein (hsCRP) level was significantly higher in patients with chronic rheumatic valve disease than in patients with prosthetic valves or in healthy subjects.30 Moreover, patients with multiple valve disease had significantly higher plasma hsCRP levels than those with single valve involvement.30 These results suggested the persistence of inflammation in rheumatic valves at chronic stages. Expression of SR-PSOX/CXCL16 in neocapillary endothelial cells and invasion of CD8+ T cells in rheumatic valves may support their findings.

In summary, cardiac expression of SR-PSOX/CXCL16 was restricted to valvular endothelium and the expression in valvular endothelium was dramatically upregulated during infective endocarditis. Moreover, SR-PSOX/CXCL16 expression was detected in neocapillaries within cardiac valves in chronic inflammatory valvular disease. The result of the present study suggested that SR-PSOX/CXCL16 might be involved in the recruitment of activated CD8+ T lymphocytes and enhancement of IFN-{gamma} production during inflammatory valvular heart disease.


*    Acknowledgments
 
Acknowledgments

We thank Noboru Ashida for his help in cell adhesion assay and Tomohiro Watanabe for his help in isolation of CD8+ T cells. This work was supported by research grants from the MEXT of Japan (grants 13045019, 13832003, 15590738, 12CE2006, and13307034) and by a grant provided by the Ichiro Kanehara Foundation.

Received July 16, 2003; accepted December 1, 2003.


*    References
up arrowTop
up arrowAbstract
up arrowIntroduction
up arrowMethods
up arrowResults
up arrowDiscussion
*References
 
1. Rossi D, Zlotnik A. The biology of chemokines and their receptors. Annu Rev Immunol. 2000; 18: 217–242.[CrossRef][Medline] [Order article via Infotrieve]

2. Mackay CR. Chemokines: immunology’s high impact factors. Nat Immunol. 2001; 2: 95–101.[CrossRef][Medline] [Order article via Infotrieve]

3. Luther SA, Cyster JG. Chemokines as regulators of T cell differentiation. Nat Immunol. 2001; 2: 102–107.[CrossRef][Medline] [Order article via Infotrieve]

4. Strieter RM, Polverini PJ, Kunkel SL, Arenberg DA, Burdick MD, Kasper J, Dzuiba J, Van Damme J, Walz A, Marriott D, Chan SY, Roczniak S, Shanafelt AB. The functional role of the ELR motif in CXC chemokine-mediated angiogenesis. J Biol Chem. 1995; 270: 27348–27357.[Abstract/Free Full Text]

5. Salcedo R, Young HA, Ponce ML, Ward JM, Kleinman HK, Murphy WJ, Oppenheim JJ. Eotaxin (CCL11) induces in vivo angiogenic responses by human CCR3+ endothelial cells. J Immunol. 2001; 166: 7571–7578.[Abstract/Free Full Text]

6. Baggiolini M. Chemokines and leukocyte traffic. Nature. 1998; 392: 565–568.[CrossRef][Medline] [Order article via Infotrieve]

7. Moser B, Loetscher P. Lymphocyte traffic control by chemokines. Nat Immunol. 2001; 2: 123–128.[CrossRef][Medline] [Order article via Infotrieve]

8. Sanchez-Madrid F, del Pozo MA. Leukocyte polarization in cell migration and immune interactions. EMBO J. 1999; 18: 501–511.[CrossRef][Medline] [Order article via Infotrieve]

9. Gerszten RE, Garcia-Zepeda EA, Lim YC, Yoshida M, Ding HA, Gimbrone MA, Jr., Luster AD, Luscinskas FW, Rosenzweig A. MCP-1 and IL-8 trigger firm adhesion of monocytes to vascular endothelium under flow conditions. Nature. 1999; 398: 718–723.[CrossRef][Medline] [Order article via Infotrieve]

10. Agace WW, Higgins JM, Sadasivan B, Brenner MB, Parker CM. T-lymphocyte-epithelial-cell interactions: integrin {alpha}(E)(CD103)ß(7), LEEP-CAM and chemokines. Curr Opin Cell Biol. 2000; 12: 563–568.[CrossRef][Medline] [Order article via Infotrieve]

11. Kunkel EJ, Butcher EC. Chemokines and the tissue-specific migration of lymphocytes. Immunity. 2002; 16: 1–4.[CrossRef][Medline] [Order article via Infotrieve]

12. Matloubian M, David A, Engel S, Ryan JE, Cyster JG. A transmembrane CXC chemokine is a ligand for HIV-coreceptor Bonzo. Nat Immunol. 2000; 1: 298–304.[CrossRef][Medline] [Order article via Infotrieve]

13. Shimaoka T, Kume N, Minami M, Hayashida K, Kataoka H, Kita T, Yonehara S. Molecular cloning of a novel scavenger receptor for oxidized low density lipoprotein, SR-PSOX, on macrophages. J Biol Chem. 2000; 275: 40663–40666.[Abstract/Free Full Text]

14. Wilbanks A, Zondlo SC, Murphy K, Mak S, Soler D, Langdon P, Andrew DP, Wu L, Briskin M. Expression cloning of the STRL33/BONZO/TYMSTR ligand reveals elements of CC, CXC, and CX3C chemokines. J Immunol. 2001; 166: 5145–5154.[Abstract/Free Full Text]

15. Shimaoka T, Nakayama T, Kume N, Takahashi S, Yamaguchi J, Minami M, Hayashida K, Kita T, Ohsumi J, Yoshie O, Yonehara S. Cutting edge: SR-PSOX/CXC chemokine ligand 16 mediates bacterial phagocytosis by APCs through its chemokine domain. J Immunol. 2003; 171: 1647–1651.[Abstract/Free Full Text]

16. Kruisbeek A. Preparation of cell suspensions from spleen, thymus and lymph node. In: Coligan JKA, Margulies D, Shewach EWS, eds. Current Protocols in Immunology. New York: Wiley; 1993.

17. Cycke N. Isolation of PP lymphocytes. In: Coligan JKA, Margulies D, Shewach EWS, eds. Current Protocols in Immunology. New York: Wiley; 1996.

18. Humphries MJ, Olden K, Yamada KM. A synthetic peptide from fibronectin inhibits experimental metastasis of murine melanoma cells. Science. 1986; 233: 467–470.[Abstract/Free Full Text]

19. Taooka Y, Chen J, Yednock T, Sheppard D. The integrin {alpha}9ß1 mediates adhesion to activated endothelial cells and transendothelial neutrophil migration through interaction with vascular cell adhesion molecule-1. J Cell Biol. 1999; 145: 413–420.[Abstract/Free Full Text]

20. Ashida N, Arai H, Yamasaki M, Kita T. Distinct signaling pathways for MCP-1-dependent integrin activation and chemotaxis. J Biol Chem. 2001; 276: 16555–16560.[Abstract/Free Full Text]

21. Mjaatvedt CH, Yamamura H, Wessels A, Ramsdell A, Turner D, Markwald R. Mechanisms of segmentation, septation, and remodeling of the tubular heart: endocardial cushion fate and cardiac looping. In: Harvey R, Rosenthal N, eds. Heart Development. San Diego: Academic Press; 1999.

22. Campbell JJ, Butcher EC. Chemokines in tissue-specific and microenvironment-specific lymphocyte homing. Curr Opin Immunol. 2000; 12: 336–341.[CrossRef][Medline] [Order article via Infotrieve]

23. Sallusto F, Lanzavecchia A, Mackay CR. Chemokines and chemokine receptors in T-cell priming and Th1/Th2-mediated responses. Immunol Today. 1998; 19: 568–574.[CrossRef][Medline] [Order article via Infotrieve]

24. Hansson GK. Immune mechanisms in atherosclerosis. Arterioscler Thromb Vasc Biol. 2001; 21: 1876–1890.[Abstract/Free Full Text]

25. Gor DO, Rose NR, Greenspan NS. TH1-TH2: a procrustean paradigm. Nat Immunol. 2003; 4: 503–505.[CrossRef][Medline] [Order article via Infotrieve]

26. Friesel R, Komoriya A, Maciag T. Inhibition of endothelial cell proliferation by gamma-interferon. J Cell Biol. 1987; 104: 689–696.[Abstract/Free Full Text]

27. Hansson GK, Hellstrand M, Rymo L, Rubbia L, Gabbiani G. Interferon gamma inhibits both proliferation and expression of differentiation-specific alpha-smooth muscle actin in arterial smooth muscle cells. J Exp Med. 1989; 170: 1595–1608.[Abstract/Free Full Text]

28. Hansson GK, Holm J. Interferon-gamma inhibits arterial stenosis after injury. Circulation. 1991; 84: 1266–1272.[Abstract/Free Full Text]

29. Cines DB, Pollak ES, Buck CA, Loscalzo J, Zimmerman GA, McEver RP, Pober JS, Wick TM, Konkle BA, Schwartz BS, Barnathan ES, McCrae KR, Hug BA, Schmidt AM, Stern DM. Endothelial cells in physiology and in the pathophysiology of vascular disorders. Blood. 1998; 91: 3527–3561.[Free Full Text]

30. Golbasi Z, Ucar O, Keles T, Sahin A, Cagli K, Camsari A, Diker E, Aydogdu S. Increased levels of high sensitive C-reactive protein in patients with chronic rheumatic valve disease: evidence of ongoing inflammation. Eur J Heart Fail. 2002; 4: 593–595.[CrossRef][Medline] [Order article via Infotrieve]




This article has been cited by other articles:


Home page
Circ Heart FailHome page
C. P. Dahl, C. Husberg, L. Gullestad, A. Waehre, J. K. Damas, L. E. Vinge, A. V. Finsen, T. Ueland, G. Florholmen, S. Aakhus, et al.
Increased Production of CXCL16 in Experimental and Clinical Heart Failure: A Possible Role in Extracellular Matrix Remodeling
Circ Heart Fail, November 1, 2009; 2(6): 624 - 632.
[Abstract] [Full Text] [PDF]


Home page
CirculationHome page
N. Kimura, C. Shukunami, D. Hakuno, M. Yoshioka, S. Miura, D. Docheva, T. Kimura, Y. Okada, G. Matsumura, T. Shin'oka, et al.
Local Tenomodulin Absence, Angiogenesis, and Matrix Metalloproteinase Activation Are Associated With the Rupture of the Chordae Tendineae Cordis
Circulation, October 21, 2008; 118(17): 1737 - 1747.
[Abstract] [Full Text] [PDF]


Home page
J. Immunol.Home page
S. Matsumura, B. Wang, N. Kawashima, S. Braunstein, M. Badura, T. O. Cameron, J. S. Babb, R. J. Schneider, S. C. Formenti, M. L. Dustin, et al.
Radiation-Induced CXCL16 Release by Breast Cancer Cells Attracts Effector T Cells
J. Immunol., September 1, 2008; 181(5): 3099 - 3107.
[Abstract] [Full Text] [PDF]


Home page
Cardiovasc ResHome page
C. Smith, B. Halvorsen, K. Otterdal, T. Waehre, A. Yndestad, B. Fevang, W. J. Sandberg, U. M. Breland, S. S. Froland, E. Oie, et al.
High levels and inflammatory effects of soluble CXC ligand 16 (CXCL16) in coronary artery disease: down-regulatory effects of statins
Cardiovasc Res, July 1, 2008; 79(1): 195 - 203.
[Abstract] [Full Text] [PDF]


Home page
Infect. Immun.Home page
H. Beekhuizen and J. S. van de Gevel
Gamma Interferon Confers Resistance to Infection with Staphylococcus aureus in Human Vascular Endothelial Cells by Cooperative Proinflammatory and Enhanced Intrinsic Antibacterial Activities
Infect. Immun., December 1, 2007; 75(12): 5615 - 5626.
[Abstract] [Full Text] [PDF]


Home page
J. Leukoc. Biol.Home page
M. Facco, I. Baesso, M. Miorin, M. Bortoli, A. Cabrelle, E. Boscaro, C. Gurrieri, L. Trentin, R. Zambello, F. Calabrese, et al.
Expression and role of CCR6/CCL20 chemokine axis in pulmonary sarcoidosis
J. Leukoc. Biol., October 1, 2007; 82(4): 946 - 955.
[Abstract] [Full Text] [PDF]


Home page
Am. J. Pathol.Home page
G. E. Garcia, L. D. Truong, P. Li, P. Zhang, R. J. Johnson, C. B. Wilson, and L. Feng
Inhibition of CXCL16 Attenuates Inflammatory and Progressive Phases of Anti-Glomerular Basement Membrane Antibody-Associated Glomerulonephritis
Am. J. Pathol., May 1, 2007; 170(5): 1485 - 1496.
[Abstract] [Full Text] [PDF]


Home page
J Am Coll CardiolHome page
M. Lehrke, S. C. Millington, M. Lefterova, R. G. Cumaranatunge, P. Szapary, R. Wilensky, D. J. Rader, M. A. Lazar, and M. P. Reilly
CXCL16 Is a Marker of Inflammation, Atherosclerosis, and Acute Coronary Syndromes in Humans
J. Am. Coll. Cardiol., January 30, 2007; 49(4): 442 - 449.
[Abstract] [Full Text] [PDF]


Home page
Int ImmunolHome page
T. Hara, T. Katakai, J.-H. Lee, Y. Nambu, N. Nakajima-Nagata, H. Gonda, M. Sugai, and A. Shimizu
A transmembrane chemokine, CXC chemokine ligand 16, expressed by lymph node fibroblastic reticular cells has the potential to regulate T cell migration and adhesion
Int. Immunol., February 1, 2006; 18(2): 301 - 311.
[Abstract] [Full Text] [PDF]


Home page
Am. J. Respir. Crit. Care Med.Home page
C. Agostini, A. Cabrelle, F. Calabrese, M. Bortoli, E. Scquizzato, S. Carraro, M. Miorin, B. Beghe, L. Trentin, R. Zambello, et al.
Role for CXCR6 and Its Ligand CXCL16 in the Pathogenesis of T-Cell Alveolitis in Sarcoidosis
Am. J. Respir. Crit. Care Med., November 15, 2005; 172(10): 1290 - 1298.
[Abstract] [Full Text] [PDF]


Home page
J. Biol. Chem.Home page
B. Chandrasekar, S. Mummidi, A. J. Valente, D. N. Patel, S. R. Bailey, G. L. Freeman, M. Hatano, T. Tokuhisa, and L. E. Jensen
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
J. Biol. Chem., July 15, 2005; 280(28): 26263 - 26277.
[Abstract] [Full Text] [PDF]


Home page
Infect. Immun.Home page
H. Xu, W. Xu, Y. Chu, Y. Gong, Z. Jiang, and S. Xiong
Involvement of Up-Regulated CXC Chemokine Ligand 16/Scavenger Receptor That Binds Phosphatidylserine and Oxidized Lipoprotein in Endotoxin-Induced Lethal Liver Injury via Regulation of T-Cell Recruitment and Adhesion
Infect. Immun., July 1, 2005; 73(7): 4007 - 4016.
[Abstract] [Full Text] [PDF]


Home page
J. Immunol.Home page
T. Sato, H. Thorlacius, B. Johnston, T. L. Staton, W. Xiang, D. R. Littman, and E. C. Butcher
Role for CXCR6 in Recruitment of Activated CD8+ Lymphocytes to Inflamed Liver
J. Immunol., January 1, 2005; 174(1): 277 - 283.
[Abstract] [Full Text] [PDF]


This Article
Right arrow Abstract Freely available
Right arrow Full Text (PDF)
Right arrow Data Supplement
Right arrow All Versions of this Article:
24/2/282    most recent
01.ATV.0000114565.42679.c6v1
Right arrow Submit a response
Right arrow Alert me when this article is cited
Right arrow Alert me when eLetters are posted
Right arrow Alert me if a correction is posted
Right arrow Citation Map
Services
Right arrow Email this article to a friend
Right arrow Similar articles in this journal
Right arrow Similar articles in PubMed
Right arrow Alert me to new issues of the journal
Right arrow Download to citation manager
Right arrowRequest Permissions
Citing Articles
Right arrow Citing Articles via HighWire
Right arrow Citing Articles via Google Scholar
Google Scholar
Right arrow Articles by Yamauchi, R.
Right arrow Articles by Kita, T.
Right arrow Search for Related Content
PubMed
Right arrow PubMed Citation
Right arrow Articles by Yamauchi, R.
Right arrow Articles by Kita, T.
Right arrowPubmed/NCBI databases
*Gene*GEO Profiles
*HomoloGene*Protein
*UniGene
*Substance via MeSH
Medline Plus Health Information
*Heart Valve Diseases
*Joint Disorders
Related Collections
Right arrow Infectious endocarditis
Right arrow Growth factors/cytokines
Right arrow Valvular heart disease
Right arrow Endothelium/vascular type/nitric oxide