Dirk Wuttge

CXCL16/SR-PSOX is an interferon-gamma-regulated chemokine and scavenger receptor expressed in atherosclerotic lesions

Objective—Atherosclerosis is an inflammatory disease. Several chemokines are important for monocyte/macrophage and T-cell recruitment to the lesion. CXCL16 is a recently discovered chemokine that is expressed in soluble and transmembrane forms, ligates CXCR6 chemokine receptor, and guides migration of activated Th1 and Tc1 cells. It is identical to scavenger receptor SR-PSOX, which mediates uptake of oxidized low-density lipoprotein. We investigated whether CXCL16 expression is controlled by interferon-&ggr; (IFN-&ggr;)-cytokine abundant in atherosclerotic lesions. Methods and Results—CXCL16 and CXCR6 expression was identified by polymerase chain reaction and histochemistry in atherosclerotic lesions from humans and apolipoprotein-E–deficient mice. In vitro IFN-&ggr; induced CXCL16 in human monocytic THP-1 cells and primary human monocytes, which led to increased uptake of oxidized low-density lipoprotein in THP-1 cells, which could be blocked by peptide antibodies against CXCL16. In vivo IFN-&ggr; induced CXCL16 expression in murine atherosclerotic lesions. Conclusions—We demonstrate a novel role of IFN-&ggr; in foam cell formation through upregulation of CXCL16/SR-PSOX. CXCR6 expression in the plaque confirms the presence of cells able to respond to CXCL16. Therefore, this chemokine/scavenger receptor could serve as a molecular link between lipid metabolism and immune activity in the atherosclerotic lesion.

Proteome-wide Analysis and CXCL4 as a Biomarker in Systemic Sclerosis

BACKGROUND Plasmacytoid dendritic cells have been implicated in the pathogenesis of systemic sclerosis through mechanisms beyond the previously suggested production of type I interferon. METHODS We isolated plasmacytoid dendritic cells from healthy persons and from patients with systemic sclerosis who had distinct clinical phenotypes. We then performed proteome-wide analysis and validated these observations in five large cohorts of patients with systemic sclerosis. Next, we compared the results with those in patients with systemic lupus erythematosus, ankylosing spondylitis, and hepatic fibrosis. We correlated plasma levels of CXCL4 protein with features of systemic sclerosis and studied the direct effects of CXCL4 in vitro and in vivo. RESULTS Proteome-wide analysis and validation showed that CXCL4 is the predominant protein secreted by plasmacytoid dendritic cells in systemic sclerosis, both in circulation and in skin. The mean (±SD) level of CXCL4 in patients with systemic sclerosis was 25,624±2652 pg per milliliter, which was significantly higher than the level in controls (92.5±77.9 pg per milliliter) and than the level in patients with systemic lupus erythematosus (1346±1011 pg per milliliter), ankylosing spondylitis (1368±1162 pg per milliliter), or liver fibrosis (1668±1263 pg per milliliter). CXCL4 levels correlated with skin and lung fibrosis and with pulmonary arterial hypertension. Among chemokines, only CXCL4 predicted the risk and progression of systemic sclerosis. In vitro, CXCL4 down-regulated expression of transcription factor FLI1, induced markers of endothelial-cell activation, and potentiated responses of toll-like receptors. In vivo, CXCL4 induced the influx of inflammatory cells and skin transcriptome changes, as in systemic sclerosis. CONCLUSIONS Levels of CXCL4 were elevated in patients with systemic sclerosis and correlated with the presence and progression of complications, such as lung fibrosis and pulmonary arterial hypertension. (Funded by the Dutch Arthritis Association and others.).

The pronounced Th17 profile in systemic sclerosis (SSc) together with intracellular expression of TGFβ and IFNγ distinguishes SSc phenotypes

Background Systemic sclerosis (SSc) is an autoimmune disease where controversy on Th1/Th2 balance dominates. We investigated whether the recently discovered Th17 pattern was present in SSc. Methodology and Principal Findings Patients were subdivided as having limited cutaneous SSc (lcSSc, n = 12) or diffuse cutaneous SSc (dcSSc, n = 24). A further arbitrary subdivision was made between early dcSSc (n = 11) and late dcSSc (n = 13) based upon the duration of disease. As a comparator group 14 healthy controls were studied. CD3+ cells were isolated using FACS and subsequently studied for the expression of CD4, CD8, CD25, CD45Ro, CD45Ra, IL-23, GITR, CD69 and intracellular expression of IL-17, TGFβ and IFNγ using flow cytometry. Levels of IL-17, IL-6, IL-1α and IL-23 were measured using Bioplex assays. SSc patients had more and more activated CD4+ cells. In addition, CD4, CD45Ro and CD45Ra cells from all SSc patients highly expressed the IL23R, which was associated with a higher IL-17 expression as well. In contrast, IFNγ and TGFβ were selectively up regulated in SSc subsets. In line with these observation, circulating levels of IL-17 inducing cytokines IL-6, IL-23 and IL-1α were increased in all or subsets of SSc patients. Conclusion and Significance The combination of IL-17, IFNγ and TGFβ levels in CD45Ro and CD45Ra cells from SSc patients is useful to distinguish between lSSc, ldSSc or edSSc. Blocking Th17 inducing cytokines such as IL-6 and IL-23 may provide a useful tool to intervene in the progression of SSc.

Differential expression of cysteine and aspartic proteases during progression of atherosclerosis in apolipoprotein E-deficient mice

Several groups of proteolytic enzymes are able to degrade components of the extracellular matrix. During atherosclerosis, matrix remodeling is believed to influence the migration and proliferation of cells within the plaque. In the present study, gene expression of several proteases and their inhibitors was analyzed during the development of atherosclerosis in apolipoprotein E-deficient (ApoE-/-) mice. Quantitative real-time polymerase chain reaction was used to study gene expression of proteases after 10 and 20 weeks in ApoE-/- and C57BL/6 mice and in atherosclerotic lesions and nonaffected regions of the same ApoE-/- mouse. Some of the differentially expressed proteolytic enzymes were studied by immunohistochemistry. The matrix metalloproteinase (MMP)-9 and its inhibitor TIMP-1 were differentially expressed and the expression increased with time. Urokinase-type plasminogen activator showed no major expression. In contrast, cathepsins B, D, L, and S all showed strong and increased expression in ApoE-/- mice compared to C57BL/6 mice whereas the expression of their inhibitor, cystatin C, did not differ between the two mouse strains. The expression of cathepsins was mainly localized to the lesions and not to nonaffected regions of the aorta of ApoE-/- mice. Furthermore, cathepsin expression was similar to the expression of the macrophage marker macrosialin (CD68) although expression of cathepsins B, D, and L could be demonstrated in healthy C57BL/6 mice and in nonaffected vessel segments of atherosclerotic ApoE-/- mice. Cathepsin S mRNA expression was restricted to lesions of ApoE-/- mice. Furthermore, cathepsin S was the only cathepsin that was expressed in the media and absent in lipid-rich regions. All cathepsins studied showed intimal expression, the degree and localization of which differed between individual cathepsins. In conclusion, increased expression of several cathepsins in atherosclerotic lesions suggests that these proteases may participate in the remodeling of extracellular matrix associated with the atherosclerotic process.

Serum Protein Profiling of Systemic Lupus Erythematosus and Systemic Sclerosis Using Recombinant Antibody Microarrays

Systemic lupus erythematosus (SLE) and systemic sclerosis (SSc) are two severe autoimmune connective tissue diseases. The fundamental knowledge about their etiology is limited and the conditions display complex pathogenesis, multifaceted presentations, and unpredictable courses. Despite significant efforts, the lack of fully validated biomarkers enabling diagnosis, classification, and monitoring of disease activity represents significant unmet clinical needs. In this discovery study, we have for the first time used recombinant antibody microarrays for miniaturized, multiplexed serum protein profiling of SLE and SSc, targeting mainly immunoregulatory proteins. The data showed that several candidate SLE-associated multiplexed serum biomarker signatures were delineated, reflecting disease (diagnosis), disease severity (phenotypic subsets), and disease activity. Selected differentially expressed markers were validated using orthogonal assays and a second, independent patient cohort. Further, biomarker signatures differentiating SLE versus SSc were demonstrated, and the observed differences increased with severity of SLE. In contrast, the data showed that the serum profiles of SSc versus healthy controls were more similar. Hence, we have shown that affinity proteomics could be used to de-convolute crude, nonfractionated serum proteomes, extracting molecular portraits of SLE and SSc, further enhancing our fundamental understanding of these complex autoimmune conditions.

Expression of interleukin-15 in mouse and human atherosclerotic lesions

Atherosclerotic lesions are characterized by prominent macrophage and T-cell infiltration and atherosclerosis is widely recognized as an inflammatory disease. The cytokine interleukin-15 (IL-15) has T-cell chemotactic and pro-inflammatory properties and promotes the recruitment of T cells to sites of inflammation. We have therefore examined IL-15 expression in the atherosclerotic ApoE-deficient mouse model as well as in human atherosclerotic lesions. In gene expression arrays, a transcript corresponding to IL-15 mRNA was elevated in atherosclerotic aortas of ApoE-deficient mice fed a Western diet for 10 and 20 weeks, corresponding to lesions of the fatty streak and fibrofatty plaque stage, respectively. Immunostaining for IL-15 localized to aortic smooth muscle cells in nonatherosclerotic C57BL/6 mice, whereas both macrophages and smooth muscle cells stained positive for IL-15 in atherosclerotic lesions of ApoE-deficient mice. Finally, advanced atherosclerotic lesions of human carotid arteries were immunostained to determine whether IL-15 is involved in human disease. IL-15 protein was present also in the human lesions with a distribution primarily overlapping that of macrophages. In conclusion, IL-15 is up-regulated in both human and animal atherosclerotic lesions and may contribute to the recruitment of T cells and their activation during atherogenesis.

Induction of CD36 by all-trans retinoic acid: retinoic acid receptor signaling in the pathogenesis of atherosclerosis

Scavenger receptors mediating the uptake of oxidized low‐density lipoproteins (oxLDL) by macrophages play a crucial role in foam cell formation during atherosclerosis. One member of this receptor family, the thrombospondin receptor CD36, has recently been shown to mediate a major part of the oxLDL‐induced aggravation of atherosclerotic lesions. Here, we show that the expression of CD36 protein and mRNA in human monocytic THP‐1 cells is increased by all‐trans retinoic acid (atRA), a derivative of the essential Vitamin A, which leads to increased uptake of oxLDL. CD3106, a specific antagonist at the retinoic acid receptor (RAR), inhibited the atRA‐induced CD36 expression, whereas the RAR‐specific agonist CD367 induced CD36 to the same degree as atRA. This indicates an RAR‐mediated CD36 induction. AtRA and oxLDL had synergistic effects in up‐regulating CD36 when in both THP‐1 cells and primary monocytes. Applying a sensitive RAR‐GAL‐4 reporter assay, we could demonstrate RAR ligands in human atherosclerotic lesions. In addition, immunohistochemistry showed RAR‐α and ‐γ in the lesions, which indicates that atRA may contribute to foam cell formation and the progress of atherosclerosis.

T-cell recognition of lipid peroxidation products breaks tolerance to self proteins

Peroxidation of polyunsaturated fatty acids in lipoproteins and cell membrane phospholipids occurs in many situations in the body, both under normal and pathological conditions. Low‐density lipoprotein is particularly prone to oxidation and is believed to be a pathogenetic component in atherogenesis. Both antibody responses and T‐cell responses to oxidatively modified lipoproteins have been demonstrated in humans as well as in animal models. However, little is known about how these responses arise or how T cells recognize these antigens. In the present study, mice were immunized with homologous albumin covalently modified with a series of defined aldehydes which are known to be generated during lipid peroxidation. T‐cell hybridomas from immunized animals demonstrated major histocompatibility complex‐restricted and protein sequence‐dependent responses to modified albumin, but not to native albumin. In addition to the response to modified epitopes, some aldehyde modifications resulted in strong antibody responses also to the non‐modified protein. This T‐cell‐dependent break of tolerance constitutes a novel pathway for induction of autoimmunity by lipid peroxidation. The findings have implications in many situations where lipid peroxidation products are generated, including atherosclerosis and inflammatory and infectious diseases.

Survival in patients with pulmonary arterial hypertension associated with systemic sclerosis from a Swedish single centre: prognosis still poor and prediction difficult

Objectives: To describe the survival rate in a cohort of systemic sclerosis (SSc) patients with pulmonary arterial hypertension (PAH) and to evaluate possible predictors for SSc-PAH in a cohort of SSc patients. Methods: Thirty patients with SSc-PAH and 150 SSc patients without PAH were included. Survival and survival on therapy were calculated. Clinical features at baseline were correlated to the risk for development of PAH during follow-up. Results: The 1-, 2-, 3-, and 4-year survival rates were 86, 59, 39, and 22%, respectively, from diagnosis of PAH. The hazard ratio for total mortality in the SSc-PAH group was 3.2 [95% confidence interval (CI) 1.8–5.7] compared to SSc without PAH (p < 0.001). Risk factors at baseline for the development of PAH were: limited skin involvement, low diffusing capacity of the lung for carbon monoxide (DLCO), high N-terminal pro-brain natriuretic peptide (NTProBNP), increased estimated systolic pulmonary arterial pressure (ESPAP), and the presence of teleangiectases. Severe peripheral vascular disease requiring iloprost treatment during follow-up was associated with an eightfold increased risk of PAH. Conclusion: Despite modern treatment and yearly screening by echocardiography, the survival in SSc-PAH is still low in our cohort. The identified risk factors should be assessed to select patients eligible for right heart catheterization (RHC) to make an earlier diagnosis.

Distinct evolution of TLR-mediated dendritic cell cytokine secretion in patients with limited and diffuse cutaneous systemic sclerosis

Background Systemic sclerosis (SSc) is an autoimmune disease and accumulating evidence suggests a role for Toll-like receptor (TLR)-mediated activation of dendritic cells (DCs). Objective To map TLR-mediated cytokine responses of DCs from patients with SSc. Methods 45 patients with SSc were included. Patients were stratified as having diffuse cutaneous SSc (dSSc) or limited cutaneous SSc (lSSc) according to the extent of skin involvement, and further divided into those with late (>3 years) or early disease (<2 years). DCs were stimulated with ligands for TLR2, TLR3, TLR4, TLR7/8 or combinations. Plasma samples were collected from patients with SSc (n=167) and measured for interleukin 6 (IL-6), tumour necrosis factor α (TNFα), IL-12, IL-10 and interferon γ. Results Stimulation of DC subsets from patients with early lSSc and dSSc with ligands for TLR2, TLR3 or TLR4 resulted in higher secretion of IL-6 and TNFα compared with those having late disease or healthy controls. Remarkably, the production of IL-12 was lower upon stimulation with TLR ligands in most patients with SSc, whereas the secretion of IL-10 was very high in patients with the dSSc phenotype, particularly in those having early dSSc. The combination of various TLR ligands led to reduced cytokine secretion in all patients with SSc. Circulating levels of these cytokines further underscored the presence of differences between various SSc phenotypes. Discussion The altered TLR-mediated activation of DCs may be responsible for Th2 skewed T-cell activation in SSc that may be orchestrated by fibrogenic T-cell cytokines, such as IL-4 and IL-13. DC targeting could thus offer new avenues for therapeutic intervention.