Sabine Rauscher

Interleukin-33 Induces Expression of Adhesion Molecules and Inflammatory Activation in Human Endothelial Cells and in Human Atherosclerotic Plaques

Objective— Interleukin (IL)-33 is the most recently described member of the IL-1 family of cytokines and it is a ligand of the ST2 receptor. While the effects of IL-33 on the immune system have been extensively studied, the properties of this cytokine in the cardiovascular system are much less investigated. Methods/Results— We show here that IL-33 promoted the adhesion of human leukocytes to monolayers of human endothelial cells and robustly increased vascular cell adhesion molecule-1, intercellular adhesion molecule-1, endothelial selectin, and monocyte chemoattractant protein-1 protein production and mRNA expression in human coronary artery and human umbilical vein endothelial cells in vitro as well as in human explanted atherosclerotic plaques ex vivo. ST2-fusion protein, but not IL-1 receptor antagonist, abolished these effects. IL-33 induced translocation of nuclear factor-&kgr;B p50 and p65 subunits to the nucleus in human coronary artery endothelial cells and human umbilical vein endothelial cells and overexpression of dominant negative form of I&kgr;B kinase 2 or I&kgr;B&agr; in human umbilical vein endothelial cells abolished IL-33-induced adhesion molecules and monocyte chemoattractant protein-1 mRNA expression. We detected IL-33 and ST2 on both protein and mRNA level in human carotid atherosclerotic plaques. Conclusion— We hypothesize that IL-33 may contribute to early events in endothelial activation characteristic for the development of atherosclerotic lesions in the vessel wall, by promoting adhesion molecules and proinflammatory cytokine expression in the endothelium.

Components of the interleukin-33/ST2 system are differentially expressed and regulated in human cardiac cells and in cells of the cardiac vasculature

Interleukin-33 (IL-33) is a recently described member of the IL-1 family of cytokines, which was identified as a ligand for the ST2 receptor. Components of the IL-33/ST2 system were shown to be expressed in normal and pressure overloaded human myocardium, and soluble ST2 (sST2) has emerged as a prognostic biomarker in myocardial infarction and heart failure. However, expression and regulation of IL-33 in human adult cardiac myocytes and fibroblasts was not tested before. In this study we found that primary human adult cardiac fibroblasts (HACF) and human adult cardiac myocytes (HACM) constitutively express nuclear IL-33 that is released during cell necrosis. Tumor necrosis factor (TNF)-α, interferon (IFN)-γ and IL-1β significantly increased both IL-33 protein and IL-33 mRNA expression in HACF and HACM as well as in human coronary artery smooth muscle cells (HCASMC). The nuclear factor-κB (NF-κB) inhibitor dimethylfumarate inhibited TNF-α- and IL-1β-induced IL-33 production as well as nuclear translocation of p50 and p65 NF-κB subunits in these cells. Mitogen-activated protein/extracellular signal-regulated kinase inhibitor U0126 abrogated TNF-α-, IFN-γ-, and IL-1β-induced and Janus-activated kinase inhibitor I reduced IFN-γ-induced IL-33 production. We detected IL-33 mRNA in human myocardial tissue from patients undergoing heart transplantation (n = 27) where IL-33 mRNA levels statistically significant correlated with IFN-γ (r = 0.591, p = 0.001) and TNF-α (r = 0.408, p = 0.035) mRNA expression. Endothelial cells in human heart expressed IL-33 as well as ST2 protein. We also reveal that human cardiac and vascular cells have different distribution patterns of ST2 isoforms (sST2 and transmembrane ST2L) mRNA expression and produce different amounts of sST2 protein. Both human macrovascular (aortic and coronary artery) and heart microvascular endothelial cells express specific mRNA for both ST2 isoforms (ST2L and sST2) and are a source for sST2 protein, whereas cardiac myocytes, cardiac fibroblasts and vascular SMC express only minor amounts of ST2 mRNA and do not secrete detectable amounts of sST2 antigen. In accordance with the cellular distribution of ST2 receptor, human cardiac fibroblasts and myocytes as well as HCASMC did not respond to treatment with IL-33, as recombinant human IL-33 did not induce NF-κB p50 and p65 subunits nuclear translocation or increase IL-6, IL-8, and monocyte chemoattractant protein (MCP-1) level in HACF, HACM and HCASMC. In summary, we found that endothelial cells seem to be the source of sST2 and the target for IL-33 in the cardiovascular system. IL-33 is expressed in the nucleus of human adult cardiac fibroblasts and myocytes and released during necrosis. Proinflammatory cytokines TNF-α, IFN-γ and IL-1β increase IL-33 in these cells in vitro, and IL-33 mRNA levels correlated with TNF-α and IFN-γ mRNA expression in human myocardial tissue.

Human but Not Mouse Adipogenesis Is Critically Dependent on LMO3

Summary Increased visceral fat is associated with a high risk of diabetes and metabolic syndrome and is in part caused by excessive glucocorticoids (GCs). However, the molecular mechanisms remain undefined. We now identify the GC-dependent gene LIM domain only 3 (LMO3) as being selectively upregulated in a depot-specific manner in human obese visceral adipose tissue, localizing primarily in the adipocyte fraction. Visceral LMO3 levels were tightly correlated with expression of 11β-hydroxysteroid dehydrogenase type-1 (HSD11B1), the enzyme responsible for local activation of GCs. In early human adipose stromal cell differentiation, GCs induced LMO3 via the GC receptor and a positive feedback mechanism involving 11βHSD1. No such induction was observed in murine adipogenesis. LMO3 overexpression promoted, while silencing of LMO3 suppressed, adipogenesis via regulation of the proadipogenic PPARγ axis. These results establish LMO3 as a regulator of human adipogenesis and could contribute a mechanism resulting in visceral-fat accumulation in obesity due to excess glucocorticoids.

Tissue factor is induced by interleukin-33 in human endothelial cells: a new link between coagulation and inflammation.

Tissue factor (TF) is the primary trigger of coagulation. Elevated levels of TF are found in atherosclerotic plaques, and TF leads to thrombus formation when released upon plaque rupture. Interleukin (IL)-33 was previously shown to induce angiogenesis and inflammatory activation of endothelial cells (ECs). Here, we investigated the impact of IL-33 on TF in human ECs, as a possible new link between inflammation and coagulation. IL-33 induced TF mRNA and protein in human umbilical vein ECs and coronary artery ECs. IL-33-induced TF expression was ST2- and NF-κB-dependent, but IL-1-independent. IL-33 also increased cell surface TF activity in ECs and TF activity in ECs-derived microparticles. IL-33-treated ECs reduced coagulation time of whole blood and plasma but not of factor VII-deficient plasma. In human carotid atherosclerotic plaques (n = 57), TF mRNA positively correlated with IL-33 mRNA expression (r = 0.691, p < 0.001). In this tissue, IL-33 and TF protein was detected in ECs and smooth muscle cells by immunofluorescence. Furthermore, IL-33 and TF protein co-localized at the site of clot formation within microvessels in plaques of patients with symptomatic carotid stenosis. Through induction of TF in ECs, IL-33 could enhance their thrombotic capacity and thereby might impact on thrombus formation in the setting of atherosclerosis.

Interleukin‐33 induces urokinase in human endothelial cells―possible impact on angiogenesis

Urokinase‐type plasminogen activator (u‐PA) plays a pivotal role in extracellular proteolysis and is thought to be critically involved in the modulation of angiogenesis. Interleukin (IL)‐33 is a member of the IL‐1 cytokine family, which is thought to act as danger signal that is released from cells after injury. IL‐33 is involved in the pathogenesis of various inflammatory diseases and previously was shown to induce angiogenesis and inflammatory activation of endothelial cells.

Melanin Pigmentation in Rat Eyes: In Vivo Imaging by Polarization-Sensitive Optical Coherence Tomography and Comparison to Histology.

PURPOSE The purpose of this study was to demonstrate polarization-sensitive optical coherence tomography (PS-OCT) for imaging pigmented structures in the posterior eye segments of albino and pigmented rats and to correlate depolarization contrast of the retinal pigment epithelium (RPE) and choroid in in vivo PS-OCT to melanin pigmentation detected in postmortem histologic serial sections. METHODS In vivo three-dimensional PS-OCT imaging was performed in adult albino and pigmented rat eyes at 70-kHz A-line rate. Degree of polarization uniformity (DOPU) fundus maps and radial DOPU profiles were generated. Postmortem histomorphologic analysis was performed in order to investigate melanin pigmentation of the RPE and choroid. Fundus pigmentation maps were extracted from histologic serial sections. Pigmentation profiles were correlated to DOPU profiles of the same eyes. RESULTS Strong depolarization was found in the RPE/choroid complex of pigmented rats, whereas the same structures exhibited uniform polarization in albino rats. The difference between the depolarization characteristics between albino and pigmented animals was statistically significant. In the fundus pigmentation maps, optical pigment density was zero in albino rat eyes. In pigmented rat eyes, a strong negative correlation between optical pigment density and DOPU was observed. CONCLUSIONS This in vivo and ex vivo investigation of posterior rat eyes indicates that melanin is the cause of depolarization in retinal PS-OCT images. It further demonstrates that melanin pigmentation in the RPE and choroid can be quantified via depolarization imaging and therefore suggests that PS-OCT is a useful tool for the noninvasive quantitative assessment of pigmentary changes in vision-threatening diseases such as age-related macular degeneration.

Human Determinants and the Role of Melanocortin-1 Receptor Variants in Melanoma Risk Independent of UV Radiation Exposure.

IMPORTANCE Despite the unquestioned relationship of UV radiation (UVR) exposure and melanoma development, UVR-independent development of melanoma has only recently been described in mice. These findings in mice highlight the importance of the genetic background of the host and could be relevant for preventive measures in humans. OBJECTIVE To study the role of the melanocortin-1 receptor (MC1R) and melanoma risk independently from UVR in a clinical setting. DESIGN, SETTING, AND PARTICIPANTS Hospital-based case-control study, including genetic testing, questionnaires, and physical data (Molecular Markers of Melanoma Study data set) including 991 melanoma patients (cases) and 800 controls. MAIN OUTCOMES AND MEASURES Association of MC1R variants and melanoma risk independent from sun exposure variables. RESULTS The 1791 participants included 991 with a diagnosis of melanoma and 800 control patients (mean [SD] age, 59.2 [15.6] years; 50.5% male). Compared with wild-type carriers, carriers of MC1R variants were at higher melanoma risk after statistically adjusting for previous UVR exposure (represented by prior sunburns and signs of actinic skin damage identified by dermatologists), age, and sex compared with wild-type carriers (≥2 variants, OR, 2.13 [95% CI, 1.66-2.75], P < .001; P for trend <.001). After adjustment for sex, age, sunburns in the past, and signs of actinic skin damage, the associations remained significant (OR, 1.65 [95% CI, 1.02-2.67] for R/R, OR, 2.63 [95% CI, 1.82-3.81] for R/r; OR, 1.83 [95% CI, 1.36-2.48] for R/0; and OR, 1.50 [95% CI, 1.01-2.21] for r/r, with P values ranging from <.001 to .04 when adjusted for facial actinic skin damage; OR, 2.36 [95% CI, 1.62-3.43] for R/r; and OR, 1.47 [95% CI, 1.08-1.99] for R/0 with P values ranging from <.001 to .01 when adjusted for dorsal actinic skin damage; and OR, 2.54 [95% CI, 1.76-3.67] for R/r, OR, 1.75 [95% CI, 1.30-2.36] for R/0; and OR, 1.50 [95% CI, 1.02-2.20] for r/r with P values ranging from <.001 to .04 when adjusted for actinic skin damage on the hands). CONCLUSIONS AND RELEVANCE Carriers of MC1R variants were at increased melanoma risk independent of their sun exposure. Further studies are required to elucidate the causes of melanoma development in these individuals.

Peripapillary rat sclera investigated in vivo with polarization-sensitive optical coherence tomography.

PURPOSE To demonstrate polarization-sensitive (PS) optical coherence tomography (OCT) for noninvasive, volumetric, and quantitative imaging of the birefringent properties of the peripapillary rat sclera; to compare the findings from PS-OCT images to state-of-the-art histomorphometric analysis of the same tissues. METHODS A high-speed PS-OCT prototype operating at 840 nm was modified for imaging the rat eye. Densely sampled PS-OCT raster scans covering an area of ~1.5 × 1.5 mm centered at the papilla were acquired in the eyes of anesthetized male Sprague-Dawley rats. Cross-sectional PS-OCT images were computed, and fundus maps displaying the birefringent properties of the sclera were analyzed. Postmortem histomorphologic analysis was performed. RESULTS Polarization-sensitive OCT enables visualization of the polarization properties of ocular tissues in vivo. The birefringent characteristics of the rat sclera were quantitatively assessed. Scleral birefringence formed a donut-shaped pattern around the papilla with significantly increased values of 0.703 ± 0.089°/μm (i.e., 1.64 × 10(-3) ± 0.2 × 10(-3); mean ± standard deviation) and 0.721 ± 0.084°/μm (i.e., 1.68 × 10(-3) ± 0.2 × 10(-3)) at an eccentricity of 0.4 mm for the left and right eyes, respectively. Birefringent axis orientation maps revealed a ring-shaped distribution around the optic nerve. Postmortem PS-OCT micrographs provided access to retinal and scleral microstructure and were compared to standard histomorphologic analysis. CONCLUSIONS Polarization-sensitive OCT enables quantitative imaging of tissue polarization properties in addition to conventional OCT imaging based on reflectivity. In the rat sclera, in vivo PS-OCT provides access to volumetric mapping of birefringence. Scleral birefringence is associated with microstructural tissue organization. Therefore, PS-OCT should prove a valuable tool for the in vivo investigation of peripapillary sclera in glaucoma.

Evidence That Cingulin Regulates Endothelial Barrier Function In Vitro and In Vivo

Objective— Cingulin is a cytoplasmic component of tight junctions. Although modulation of cingulin levels in cultured epithelial model systems has no significant effect on barrier function, evidence from cingulin knockout mice suggests that cingulin may be involved in the regulation of the behavior of epithelial or endothelial cells. Here, we investigate the role of cingulin in the barrier function of endothelial cells. Approach and Results— We show that cingulin is expressed in human endothelial cells of the skin, brain, and lung in vivo and in vitro. Endothelial cingulin colocalizes and coimmunoprecipitates with the tight junction proteins zonula occludens-1 and guanine nucleotide exchange factor-H1. Cingulin overexpression in human umbilical vein endothelial cell induces tight junction formation, increases transendothelial electric resistance, and strengthens barrier function for low and high molecular weight tracers. In contrast, cultured endothelial cells lacking cingulin are more permeable for low molecular weight tracers. In cingulin knockout mice, neurons of the area postrema and Purkinje cells show an increased uptake of small molecular weight tracers indicating decreased barrier function at these sites. Conclusions— We demonstrate that cingulin participates in the modulation of endothelial barrier function both in human cultured cells in vitro and in mouse brains in vivo. Understanding the role of cingulin in maintaining tight barriers in endothelia may allow developing new strategies for the treatment of vascular leak syndromes.

Polarization properties of single layers in the posterior eyes of mice and rats investigated using high resolution polarization sensitive optical coherence tomography

We present a high resolution polarization sensitive optical coherence tomography (PS-OCT) system for ocular imaging in rodents. The system operates at 840 nm and uses a broadband superluminescent diode providing an axial resolution of 5.1 µm in air. PS-OCT data was acquired at 83 kHz A-scan rate by two identical custom-made spectrometers for orthogonal polarization states. Pigmented (Brown Norway, Long Evans) and non-pigmented (Sprague Dawley) rats as well as pigmented mice (C57BL/6) were imaged. Melanin pigment related depolarization was analyzed in the retinal pigment epithelium (RPE) and choroid of these animals using the degree of polarization uniformity (DOPU). For all rat strains, significant differences between RPE and choroidal depolarization were observed. In contrast, DOPU characteristics of RPE and choroid were similar for C57BL/6 mice. Moreover, the depolarization within the same tissue type varied significantly between different rodent strains. Retinal nerve fiber layer thickness, phase retardation, and birefringence were mapped and quantitatively measured in Long Evans rats in vivo for the first time. In a circumpapillary annulus, retinal nerve fiber layer birefringence amounted to 0.16°/µm ± 0.02°/µm and 0.17°/µm ± 0.01°/µm for the left and right eyes, respectively.