Carl Walter Steiner

Depletion of Endothelial Progenitor Cells in the Peripheral Blood of Patients With Rheumatoid Arthritis

Background—Rheumatoid arthritis (RA) is characterized by increased cardiovascular morbidity and mortality that cannot be explained solely by traditional cardiovascular risk factors. Cardiovascular morbidity is related to disease activity and can be normalized by effective therapy. Because the quantity of endothelial progenitor cells (EPCs) in the peripheral blood is correlated inversely with cardiovascular risk, we studied whether such abnormalities could also be observed in patients with RA. Methods and Results—EPCs were determined in 52 RA patients and in 16 healthy referents (HRs) by fluorescence-activated cell-sorting (FACS) analysis. Patients were divided into groups characterized by active disease (n=36) and low disease activity (n=16). Cells that were positive by flow cytometry for CD34/KDR/AC133 within the lymphocyte population were characterized as EPCs. Furthermore, in subgroups of patients, circulating EPCs were also quantified by a colony-forming unit (CFU) and a circulating angiogenic cell (CAC) assay. EPCs were significantly decreased in RA patients suffering from active disease compared with those from HRs, as measured by FACS analysis (0.026±0.002% versus 0.045±0.008%, respectively, P<0.05), CFU assay (mean of 5±2 versus 18±5 CFU/well in HRs, P<0.05), and CAC assay (mean of 7±2 versus 52±16 positive cells/high-power field, P<0.005). In contrast, the frequency of circulating EPCs from patients with low disease activity was comparable to that of healthy individuals (0.052±0.006% by FACS analysis), CFU assay (10±5 CFU/well), and CAC assay (mean of 25±5 positive cells). Moreover, EPC quantities in peripheral blood were correlated inversely with disease activity as assessed by the disease activity score (r=−0.38, P<0.01). Conclusions—Our observations indicate that active RA is associated with a depletion of circulating EPCs. This might be one of several factors contributing to the increased cardiovascular risk in RA.

Quantitative and qualitative deficiencies of regulatory T cells in patients with systemic lupus erythematosus (SLE)

The objective of the study was that the regulatory T cells (Treg) that specialize in the suppression of immune responses might be critically involved in the pathogenesis of autoimmune disease. As for systemic lupus erythematosus (SLE), however, published data concerning Treg phenotype and function are partly conflicting. We therefore performed quantitative and qualitative analyses of naturally occurring CD4(+)CD25(+) Treg from SLE patients as compared with healthy controls (HC) in order to further elucidate the role of Treg in this systemic autoimmune disease. The phenotype of peripheral blood CD4(+)CD25(+) Treg was determined by flow cytometry (FACS) in SLE patients and HC. Treg were isolated from SLE patients and HC and their functional capacity was analyzed in suppression assays. Phenotypic and functional data were correlated with clinical data. Decreased proportions of CD4(+) Treg with high-level expression of CD25 (CD4(+)CD25(hi)) were observed in active and inactive SLE patients (0.96 +/- 0.08 and 1.17 +/- 0.08%, respectively) as compared with HC (2 +/- 0.1%). In contrast to HC, Treg from SLE patients displayed an activated phenotype as determined by the expression of CD69, CD71 and HLA-DR. The suppressive capacity of isolated Treg from SLE patients, however, was significantly reduced as compared with HC. Proportions of CD4(+)CD25(hi) T cells and the suppressive capacity of Treg were inversely correlated with the clinical disease activity in SLE patients. Our data describe quantitative and qualitative defects of Treg in SLE patients. These deficiencies might contribute to the breakdown of self-tolerance and the development of the autoimmune response in SLE patients.

Activation of the interferon‐γ signaling pathway in systemic lupus erythematosus peripheral blood mononuclear cells

OBJECTIVE To investigate interferon-gamma (IFNgamma) signaling in peripheral blood mononuclear cells (PBMCs) from patients with systemic lupus erythematosus (SLE) by analyzing IFNgamma receptor (IFNgammaR) expression, STAT-1 expression and phosphorylation, and the regulation of IFNgamma-inducible genes. METHODS Fluorocytometry was used to investigate expression of STAT-1, pSTAT-1, CD95, HLA-DR, class I major histocompatibility complex (MHC), IFNgamma-inducible 10-kd protein (IP-10), monokine induced by IFNgamma (Mig), and IFNgammaR in PBMCs from SLE patients and healthy individuals. STAT-1 phosphorylation was determined by fluorocytometry and Western blotting after stimulation with IFNalpha or IFNgamma. Quantitative polymerase chain reaction was used to assess messenger RNA (mRNA) expression of the IFNgamma-inducible genes IP-10 and Mig shortly after preparation or after stimulation with IFNgamma in monocytes. RESULTS STAT-1 expression was increased in PBMCs from SLE patients and correlated significantly with disease activity and with the IFN-inducible expression of CD95 and HLA-DR. STAT-1 expression also showed a trend toward association with class I MHC expression. In addition, the expression of other IFNgamma-inducible genes, such as IP-10 or Mig, was increased in SLE monocytes. While STAT-1 phosphorylation in SLE PBMCs and PBMCs from healthy individuals was similar after IFNalpha stimulation, incubation with IFNgamma induced STAT-1 phosphorylation only in SLE lymphocytes. Moreover, SLE monocytes showed a considerably higher increase in pSTAT-1 expression upon IFNgamma stimulation than monocytes from healthy individuals. Increased responsiveness of SLE monocytes to IFNgamma was also confirmed on the mRNA level, where expression of the IFN-inducible, STAT-1-dependent genes IP-10 and Mig was more efficiently increased in SLE cells. However, IFNgammaR was similarly expressed on SLE lymphocytes and monocytes and those from healthy individuals. CONCLUSION In addition to supporting the role of IFNs in SLE immunopathogenesis in general, the findings of the present study support a role of IFNgamma in this disease.

Enhanced Lymph Vessel Density, Remodeling, and Inflammation Are Reflected by Gene Expression Signatures in Dermal Lymphatic Endothelial Cells in Type 2 Diabetes

Type 2 diabetes is associated with microvascular damage that causes frequent infections in the skin and chronic ulcers as a result of impaired wound healing. To trace the pathological changes, we performed a comprehensive analysis of lymphatic vessels in the skin of type 2 diabetic versus nondiabetic patients. The dermis revealed enhanced lymphatic vessel density, and transcriptional profiling of ex vivo isolated lymphatic endothelial cells (LECs) identified 160 genes differentially expressed between type 2 diabetic and nondiabetic LECs. Bioinformatic analysis of deregulated genes uncovered sets functionally related to inflammation, lymphatic vessel remodeling, lymphangiogenesis, and lipid and small molecule transport. Furthermore, we traced CD68+ macrophage accumulation and concomitant upregulation of tumor necrosis factor-α (TNF-α) levels in type 2 diabetic skin. TNF-α treatment of LECs and its specific blockade in vitro reproduced differential regulation of a gene set that led to enhanced LEC mobility and macrophage attachment, which was mediated by the LEC-derived chemokine CXCL10. This study identifies lymph vessel gene signatures directly correlated with type 2 diabetes skin manifestations. In addition, we provide evidence for paracrine cross-talk fostering macrophage recruitment to LECs as one pathophysiological process that might contribute to aberrant lymphangiogenesis and persistent inflammation in the skin.

Regulatory T cells form stable and long-lasting cell cluster with myeloid dendritic cells (DC)

Regulatory T cells (Treg) with the capacity to suppress T-cell proliferation exert various effects on T cell function. In addition, Treg have been shown to modulate the phenotype and function of antigen-presenting cells (APC) including dendritic cells (DC), B cells and monocytes/macrophages. However, the specific mechanism(s) of how Treg affect APC have not been entirely identified so far. In this study, we analyzed the interaction of human Treg and effector T cells (Teff) with peripheral blood myeloid and monocyte-derived dendritic cells in vitro. A strong tendency for cell cluster formation between Treg and DC was observed, which was dependent on the adhesion molecules ICAM-1, LFA-3 and ICAM-3. In addition, Treg were found to express higher levels of LFA-1, LFA-2, LFA-3 and ICAM-3 both before and after activation with anti-CD3 antibodies. Using in vitro live cell imaging, we were further able to show that Treg-DC cell clusters, in contrast to Teff-DC clusters, were stable and long lasting. Co-cultures of DC with Treg diminished the up-regulation of activation induced costimulatory molecule expression on DC, and further reduced the production of tumor necrosis factor alpha and stimulated the production of IL-4. In summary, our data indicate that Treg-DC cluster formation might enable Treg to modulate phenotypic and functional characteristics of DC and help to constrain Teff activation.

Engulfed cell remnants, and not cells undergoing apoptosis, constitute the LE-cell phenomenon

The LE cell has been one of the first immunological signs of active systemic lupus erythematosus, included into the ACR criteria. LE cells consist of a phagocyte engulfing material of disputed origin, which was interpreted as either cellular remnants from necrotic cells or as early apoptotic cells. It is well established that LE cell formation is dependent on autoantibodies against the linker histone H1. In view of this fact, we investigated whether anti-histone H1 antibodies and LE cell positive sera bound to cells where apoptosis had been induced by gliotoxin or actinomycin D or which were necrotic after heating. Necrotic cell remnants, but not (early) apoptotic cells were bound by anti-histone H1 antibodies and LE cell positive sera, establishing that the process of LE cell formation, which is dependent on anti-H1 binding, leads to engulfment of necrotic (or late apoptotic) material, but not of early apoptotic cells.

Sensitisation of the IFNγ-Stat1-signalling-pathway in rheumatoid arthritis monocytes

Background Both, type I interferons (IFNα, IFNβ) and the type II IFN IFNγ signal via phosphorylating Stat1. Immunohistochemistry and gene expression signatures of synovial tissues suggest an activated IFN-Stat1-signalling-pathway in rheumatoid arthritis (RA). This study was performed to determine the activity of the IFN-Stat1-signalling-pathway in RA peripheral blood monocytes. Methods Flourocytometry or qPCR was used to measure the expression of Stat1, phospho-Stat1 (pStat1) and IFN-inducible genes, such as IP-10 and OAS in RA and healthy (HC) peripheral blood monocytes. To examine the significance of Stat1 and of the IFNγ-inducible chemokine MIG (monokine induced by IFNγ) were measured using fluorocytometry. Results Levels of Stat1 and pStat1 protein expression were significantly increased in RA monocytes when compared to HC (mfi 14.7±8.1 vs 8.0±3.9, p=0.0002; mfi 5.1±1.3 vs 3.2±0.7, p<0.0001, respectively). Stat1 mfi in RA monocytes correlated with RA disease activity such as DAS28 (Disease Activity Score; r=0.47, p<0.008) or CDAI (Clinical Disease Activity Index; r=0.51, p<0.003). Further, Stat1 mRNA expression in RA monocytes correlated with the expression of other IFN target genes, such as IP-10 or OAS. RA monocytes demonstrated a considerably higher increase in pStat1 and MIG levels upon IFNγ stimulation when compared to monocytes from HC (pStat1: +2.8±1.8 vs +1.5±1.1, p<0.03; MIG: +565±351 vs +303±253, p<0.05), indicating that RA monocytes are more sensitive to IFNγ stimulation. Conclusions Consistent with a systemic proinflammatory activity of RA monocytes, these studies suggest activation of the IFNγ-Stat1-signalling pathway in RA.