Rusan Catar

Involvement of functional autoantibodies against vascular receptors in systemic sclerosis

Background Systemic sclerosis (SSc) features autoimmunity, vasculopathy and tissue fibrosis. The renin-angiotensin and endothelin systems have been implicated in vasculopathy and fibrosis. A role for autoantibody-mediated receptor stimulation is hypothesised, linking three major pathophysiological features consistent with SSc. Methods Serum samples from 478 patients with SSc (298 in the study cohort and 180 from two further independent cohorts), 372 healthy subjects and 311 control-disease subjects were tested for antibodies against angiotensin II type 1 receptor (AT1R) and endothelin-1 type A receptor (ETAR) by solid phase assay. Binding specificities were tested by immunoprecipitation. The biological effects of autoantibodies in microvascular endothelial cells in vitro were also determined, as well as the quantitative differences in autoantibody levels on specific organ involvements and their predictive value for SSc-related mortality. Results Anti-AT1R and anti-ETAR autoantibodies were detected in most patients with SSc. Autoantibodies specifically bound to respective receptors on endothelial cells. Higher levels of both autoantibodies were associated with more severe disease manifestations and predicted SSc-related mortality. Both autoantibodies exert biological effects as they induced extracellular signal-regulated kinase 1/2 phosphorylation and increased transforming growth factor β gene expression in endothelial cells which could be blocked with specific receptor antagonists. Conclusions Functional autoimmunity directed at AT1R and ETAR is common in patients with SSc. AT1R and ETAR autoantibodies could contribute to disease pathogenesis and may serve as biomarkers for risk assessment of disease progression.

Non-HLA antibodies in solid organ transplantation: recent concepts and clinical relevance.

Purpose of review Humoral responses beyond major histocompatibility antigens continue to receive the attention of the transplantation community. We report on clinical studies testing clinical relevance of non-human leukocyte antigen (HLA) antigens in solid organ transplantation and provide an update on novel experimental findings. A conceptual framework on the role of graft microenvironment during initiation of non-HLA-related humoral immunity is addressed as well. Recent findings Clinical relevance of antibodies targeting angiotensin type 1 receptor (AT1R-Abs) is broadly confirmed in renal and cardiac transplantation, where in addition antibodies against endothelin type A receptor (ETAR-Abs) were found. Obliterative lesions in lung allografts occur more commonly in the presence of antibodies directed against K-&agr; 1 tubulin and collagen-V. Anti-perlecan antibodies are newly identified as accelerators of obliterative vascular lesions. Changes in the intragraft microenvironment, ischemia and alloimmunity seem to represent important permissive factors for non-HLA antibody responses. Summary Confirmed clinical relevance of non-HLA humoral responses in solid organ transplantation emphasizes the need for revision of classical diagnostic approaches based solely on detection of HLA-donor-specific antibodies (DSA). A better understanding of intersections of HLA- and non-HLA-related mechanisms and identification of common effector mechanisms would represent an important step towards targeted therapies.

Role of non-HLA antibodies in organ transplantation.

Purpose of reviewHumoral responses beyond major histocompatibility antigens receive an increased attention of the transplantation community. We aimed to summarize the data on discovery of new antigenic targets, novel experimental findings, recent diagnostic developments, and introduction of new technologies in the field of non-HLA antigens in solid organ transplantation. Recent findingsNon-HLA antibodies can be currently reliably detected by solid-phase assays (MICA, angiotensin type 1 receptor, collagen-V, vimentin), immunofluorescence (antibodies against antigens expressed on umbilical vein endothelial cells), or flow-crossmatch techniques (antibodies against donor endothelial progenitors). Influence of test positivity on transplant outcomes is variable and differs among non-HLA targets. Use of omics approach helped to identify a unique set of antigens in adult and pediatric patients with severe rejections and transplant glomerulopathy. SummaryParadigms for effective monitoring of non-HLA humoral responses need to be established in order to utilize advances provided by the rapid diagnostic developments. A systematic longitudinal assessment of pretransplant sensitization together with monitoring of posttransplant changes would represent an important step forward.

Oxidative stress-dependent increase in ICAM-1 expression promotes adhesion of colorectal and pancreatic cancers to the senescent peritoneal mesothelium.

Intercellular adhesion molecule‐1 (ICAM‐1) has been implicated in adhesion of colorectal and pancreatic cancer cells (of the SW480 and PSN‐1 line, respectively) to the peritoneal mesothelium. It has been demonstrated that ICAM‐1 expression increases with senescence in some cell types, however, the significance of this phenomenon in the context of malignant dissemination remains elusive. In this report we show that the adherence of SW480 and PSN‐1 cells to senescent human omentum‐derived mesothelial cells (HOMCs) in vitro is greater than to early‐passage cells and that the effect is mediated by ICAM‐1. Senescent HOMCs display increased expression of ICAM‐1 mRNA and cell surface protein. The development of this phenotype is related to increased oxidative stress in senescent cells. The augmented ICAM‐1 expression in HOMCs can be reduced by culturing cells with antioxidants; in contrast, exposure of HOMCs to an oxidant, t‐BHP, leads to cellular senescence and increased ICAM‐1 expression. The effect is partly mediated by activation of p38 MAPK and AP‐1 signaling pathways. Finally, culture of HOMCs in the presence of a strong antioxidant, PBN, significantly reduces the senescence‐associated increase in SW480 and PSN‐1 cancer cell binding. These results indicate that increased oxidative stress and increased expression of ICAM‐1 in senescent HOMCs may facilitate peritoneal adhesion of selected colorectal and pancreatic cancers.

Non-HLA-antibodies targeting Angiotensin type 1 receptor and antibody mediated rejection.

Antibody-mediated mechanisms directed against non-HLA related targets may exert negative impact on allograft function and survival. Angiotensin type 1 receptor (AT(1)R) emerges as a functional target for non-HLA allo- and autoantibodies (AT(1)R-Abs) comprising of IgG1 and IgG3 subclasses. Proof of concept for pathophysiologic relevance of AT(1)R-Abs in antibody mediated rejection (AMR) in renal transplants was provided by passive transfer studies in animal model and therapeutic rescue of patients. Although AT(1)R-Abs may belong to complement fixing IgG subclasses, C4d positivity in renal transplant biopsies was not frequently detected implicating complement independent mechanisms of injury. AT(1)R-Abs exert direct effects on endothelial and vascular smooth muscle cells by induction of Erk1/2 signaling and increased DNA binding of transcription factors associated with pro-inflammatory and pro-coagulatory responses. Establishment of enzyme-linked immunosorbent assay employing extracts of cells overexpressing AT(1)R in its native conformation was instrumental for recent studies in independent cohorts. Assessing the AT(1)R-Ab-status along with the HLA-antibodies may help to identify patients at particular risk for irreversible acute or chronic allograft injuries and improve overall outcomes. This review summarizes the current state of research in AT(1)R biology, development in diagnostic strategies, discusses recent clinical studies, and provides perspectives on further refinements in understanding AT(1)R-Ab-actions.

Estrogen Receptor-β Signals Left Ventricular Hypertrophy Sex Differences in Normotensive Deoxycorticosterone Acetate-Salt Mice

We found earlier that deoxycorticosterone acetate-salt treatment causes blood pressure–independent left ventricular hypertrophy, but only in male mice. To test the hypothesis that the estrogen receptor-&bgr; (ER&bgr;) protects the females from left ventricular hypertrophy, we treated male and female ER&bgr;-deficient (ER&bgr;−/−) mice and their male and female littermates (wild-type [WT]) with deoxycorticosterone acetate-salt and made them telemetrically normotensive with hydralazine. WT males had increased (+16%) heart weight/tibia length ratios compared with WT females (+7%) at 6 weeks. In ER&bgr;−/− mice, this situation was reversed. Female WT mice had the greatest heart weight/tibia length ratio increases of all of the groups (+23%), even greater than ER&bgr;−/− males (+10%). Echocardiography revealed concentric left ventricular hypertrophy in male WT mice, whereas ER&bgr;−/− females developed dilative left ventricular hypertrophy. The hypertrophic response in female ER&bgr;−/− mice was accompanied by the highest degree of collagen deposition, indicating maladaptive remodeling. ER&bgr;+/+ females showed robust protective p38 and extracellular signal–regulated kinase 1/2 signaling relationships compared with other groups. Calcineurin A&bgr; expression and its positive regulator myocyte-enriched calcineurin-interacting protein 1 were increased in deoxycorticosterone acetate-salt female ER&bgr;−/− mice, yet lower than in WT males. Endothelin increased murine cardiomyocyte hypertrophy in vitro, which could be blocked by estradiol and an ER&bgr; agonist. We conclude that a functional ER&bgr; is essential for inducing adaptive p38 and extracellular signal–regulated kinase signaling, while reducing maladaptive calcineurin signaling in normotensive deoxycorticosterone acetate female mice. Our findings address the possibility of sex-specific cardiovascular therapies.

Autoimmune mediated G-protein receptor activation in cardiovascular and renal pathologies

Antibodies directed against G-protein coupled receptors (GPCR) can act as allosteric receptor agonists or antagonists. Prototypic disease for agonistic antibody action is a Graves disease of the thyroid gland where antibodies that stimulate G-protein coupled thyroid-stimulating hormone receptor (TSHR) were first described 50 years ago. Myasthenia gravis is the prototype for antagonistic autoimmune actions, where antibodies directed against the nicotinic acetylcholine receptor (AChR) cause blockade of neuromuscular junctions. Antibodies and B-cells are increasingly recognised as major modulators of various cardiovascular and renal pathologies. We aim to critically review the notion that antibodies targeting other GPCRs may amplify or cause various cardiovascular and renal pathologies and summarise the current state of research, as well as perspectives in diagnostic and therapeutic strategies. In terms of targets we will focus on the alpha-adrenergic receptor (alpha(1)AR), the beta-adrenergic receptor (beta(1)AR), and the angiotensin II type 1 receptor (AT(1)R).

The proto-oncogene c-Fos transcriptionally regulates VEGF production during peritoneal inflammation

Vascular endothelial growth factor (VEGF) and transforming growth factor-β1 (TGF-β1) are key mediators of adverse peritoneal membrane remodeling in peritoneal dialysis eventually leading to ultrafiltration failure. Both are pleiotropic growth factors with cell type-dependent regulation of expression and biological effects. Here we studied regulation of TGF-β1-induced VEGF expression in human peritoneal mesothelial cells in the absence or presence of proinflammatory stimuli, tumor necrosis factor-α (TNF-α) or interleukin-1β (IL-1β). Quiescent human peritoneal mesothelial cells secreted only trace amounts of VEGF. Stimulation with TGF-β1 resulted in time- and dose-dependent increases in VEGF mRNA expression and protein release. TNF-α and IL-1β alone had minimal effects but acted in synergy with TGF-β1. Combined stimulation led to induction of transcription factor c-Fos and activation of the VEGF promoter region with high-affinity binding sites for c-Fos. Inhibition of c-Fos by small interfering RNA interference or by pharmacological blockade with SR-11302 decreased VEGF promoter activity and downregulated its expression and release. Exposure of human peritoneal mesothelial cells to dialysate effluent containing increased levels of TGF-β1, TNF-α, and IL-1β obtained during peritonitis resulted in a dose-dependent VEGF induction that was significantly attenuated by SR-11302. Thus, dialysate TGF-β1, IL-1β, and TNF-α act through c-Fos to synergistically upregulate VEGF production in peritoneal mesothelium and may represent an important regulatory link between inflammation and angiogenesis in the peritoneal membrane.

Different Procoagulant Activity of Therapeutic Mesenchymal Stromal Cells Derived from Bone Marrow and Placental Decidua.

While therapeutic mesenchymal stromal/stem cells (MSCs) have usually been obtained from bone marrow, perinatal tissues have emerged as promising new sources of cells for stromal cell therapy. In this study, we present a first safety follow-up on our clinical experience with placenta-derived decidual stromal cells (DSCs), used as supportive immunomodulatory and regenerative therapy for patients with severe complications after allogeneic hematopoietic stem cell transplantation (HSCT). We found that DSCs are smaller, almost half the volume of MSCs, which may favor microvascular passage. DSCs also show different hemocompatibility, with increased triggering of the clotting cascade after exposure to human blood and plasma in vitro. After infusion of DSCs in HSCT patients, we observed a weak activation of the fibrinolytic system, but the other blood activation markers remained stable, excluding major adverse events. Expression profiling identified differential levels of key factors implicated in regulation of hemostasis, such as a lack of prostacyclin synthase and increased tissue factor expression in DSCs, suggesting that these cells have intrinsic blood-activating properties. The stronger triggering of the clotting cascade by DSCs could be antagonized by optimizing the cell graft reconstitution before infusion, for example, by use of low-dose heparin anticoagulant in the cell infusion buffer. We conclude that DSCs are smaller and have stronger hemostatic properties than MSCs, thus triggering stronger activation of the clotting system, which can be antagonized by optimizing the cell graft preparation before infusion. Our results highlight the importance of hemocompatibility safety testing for every novel cell therapy product before clinical use, when applied using systemic delivery.

Aldosterone Rapidly Induces Leukocyte Adhesion to Endothelial Cells: A New Link Between Aldosterone and Arteriosclerosis?

To the Editor: Aldosterone is known to induce cardiovascular dysfunction, including fibrosis, inflammation, and endothelial dysfunction, as well as thrombosis formation.1 Clinical trials have shown aldosterone to be an independent predictor of increased mortality in patients with chronic heart failure,2 and high circulating plasma aldosterone levels predict the clinical outcome in patients after myocardial infarction.3 Mineralocorticoid receptor blockade proved to exert beneficial effects in clinical trials, such as the Randomised Aldactone Evaluation Study and the Eplerenone Post-Acute Myocardial Infarction Heart Failure Efficacy and Survival Study.4 Recent studies provided evidence for a role of aldosterone in the pathogenesis of arteriosclerosis.5 However, the exact mechanisms of adverse aldosterone actions in the cardiovascular system are largely unknown. Here, we aimed at elucidating rapid (60 minutes) aldosterone effects on interactions between endothelial cells and leukocytes. …