Christian Erbel

Inhibition of IL-17A Attenuates Atherosclerotic Lesion Development in ApoE-Deficient Mice

The importance of an (auto)immune response in atherogenesis is becoming increasingly well understood. IL-17A-expressing T cells modulate immune cell trafficking, initiating inflammation and cytokine production in (auto)immune diseases. In human carotid artery plaques, we previously showed the presence of IL-17A-producing T cells and IL-23; however, IL-17A effects on atherogenesis have not been studied. Aortic root sections from 8-wk-old apolipoprotein E-deficient mice fed a standard chow diet were examined after 12 wk for lesion area, plaque composition, cellular infiltration, cytokine expression, and apoptosis. The treatment group (n = 15) received anti-IL-17A Ab and the controls (n = 10) received irrelevant Abs. Inhibition of IL-17A markedly reduced atherosclerotic lesion area (p < 0.001), maximal stenosis (p < 0.001), and vulnerability of the lesion. IL-17A mAb-treated mice showed reduced cellular infiltration, down-regulation of activation markers on endothelium and immune cells (e.g., VCAM-1), and reduced cytokine/chemokine secretion (e.g., IL6, TNFα, CCL5). To investigate possible mechanisms, different atherogenic cell types (e.g., macrophages, dendritic cells, HUVECs, vascular smooth muscle cells) were stimulated with IL-17A in addition to TNF-α, IFN-γ, or LPS to induce cellular activation or apoptosis in vitro. Stimulation with IL-17A induced proinflammatory changes in several atherogenic cell types and apoptotic cell death in murine cells. Functional blockade of IL-17A reduces atherosclerotic lesion development and decreases plaque vulnerability, cellular infiltration, and tissue activation in apolipoprotein E-deficient mice. The present data support a pathogenic role of IL-17A in the development of atherosclerosis by way of its widespread proinflammatory and proapoptotic effects on atherogenic cells.

Functional profile of activated dendriticcells in unstable atherosclerotic plaque

AbstractBackgroundUnstable atherosclerotic plaque typically contains an infiltrate of activated macrophages and activated T cells. This study established a functional profile of plaque-residing dendritic cells (DC) to examine whether they can function as Ag-presenting cells to facilitate in situ T-cell activation.MethodsCarotid artery plaque tissues were collected from 19 asymptomatic and 38 symptomatic patients undergoing endarterectomy. Matched samples of normal coronary artery wall, stable nonruptured plaque, and eroded unstable plaque were harvested from patients with fatal myocardial infarction. Quantitative PCR and immunohistochemistry were used to analyze the tissues for markers of DC activation (CD83, CD86, CCL19,CCL21) and correlate them with T-cell activation (IFN-γ,TNF-α).ResultsCarotid artery plaques from patients with ischemic symptoms compared to asymptomatic patients were characterized by the presence of high amount of T-cells (P < 0.01) and tissue production of high levels of the T-cell cytokines IFN-γ (P = 0.001) and TNF-α (P = 0.006). Plaque tissues from patients with ischemic complications contained elevated levels of CD83 (P < 0.001), a marker of DC activation, and the DC chemokines CCL19 (P = 0.001) and CCL21 (P < 0.02).Unstable coronary artery plaques were similarly correlated compared to carotid plaques from symptomatic patients with the accumulation of T cells (P = 0.001) and the production of T cell chemokines IFN-γ (P = 0.001) and TNF-α (P = 0.002).Immunohistochemistry confirmed the presence of CD83+ DC in the shoulder region of unstable plaques, where they produced the T cell-attracting chemokines CCL19 and CCL21. Mapping of activated DC demonstrated close contact between mature DC and T cells expressing the activation marker CD40 ligand (CD40L).ConclusionActivated and fully mature DC are represented in the inflammatory infiltrate characteristic for unstable carotid and coronary atheroma. Such DC produce chemokines, and thus can regulate the cell traffic into the lesion. Through the expression of the costimulatory ligand CD86, plaque-residing DC can augment T-cell stimulation and provide optimal stimulation conditions for T lymphocytes, resembling the microenvironment in organized lymphoid tissues.

CXCL4 Downregulates the Atheroprotective Hemoglobin Receptor CD163 in Human Macrophages

Rationale: CXCL4 is a platelet-derived chemokine that promotes macrophage differentiation from monocytes. Deletion of the PF4 gene that encodes CXCL4 reduces atherosclerotic lesions in ApoE−/− mice. Objective: We sought to study effects of CXCL4 on macrophage differentiation with possible relevance for atherogenesis. Methods and Results: Flow cytometry for expression of surface markers in macrophage colony–stimulating factor (M-CSF)– and CXCL4-induced macrophages demonstrated virtually complete absence of the hemoglobin scavenger receptor CD163 in CXCL4-induced macrophages. mRNA for CD163 was downregulated as early as 2 hours after CXCL4. CD163 protein reached a minimum after 3 days, which was not reversed by treatment of cells with M-CSF. The CXCL4 effect was entirely neutralized by heparin, which bound CXCL4 and prevented CXCL4 surface binding to monocytes. Pretreatment of cells with chlorate, which inhibits glycosaminoglycan synthesis, strongly inhibited CXCL4-dependent downregulation of CD163. Similar to recombinant CXCL4, releasate from human platelets also reduced CD163 expression. CXCL4-differentiated macrophages were unable to upregulate the atheroprotective enzyme heme oxygenase-1 at the RNA and protein level in response to hemoglobin–haptoglobin complexes. Immunofluorescence of human atherosclerotic plaques demonstrated presence of both CD68+CD163+ and CD68+CD163− macrophages. PF4 and CD163 gene expression within human atherosclerotic lesions were inversely correlated, supporting the in vivo relevance of CXCL4-induced downregulation of CD163. Conclusions: CXCL4 may promote atherogenesis by suppressing CD163 in macrophages, which are then unable to upregulate the atheroprotective enzyme heme oxygenase-1 in response to hemoglobin.

IL-17A Influences Essential Functions of the Monocyte/Macrophage Lineage and Is Involved in Advanced Murine and Human Atherosclerosis

Atherosclerosis is a chronic inflammatory disease. Lesion progression is primarily mediated by cells of the monocyte/macrophage lineage. IL-17A is a proinflammatory cytokine, which modulates immune cell trafficking and is involved inflammation in (auto)immune and infectious diseases. But the role of IL-17A still remains controversial. In the current study, we investigated effects of IL-17A on advanced murine and human atherosclerosis, the common disease phenotype in clinical care. The 26-wk-old apolipoprotein E–deficient mice were fed a standard chow diet and treated either with IL-17A mAb (n = 15) or irrelevant Ig (n = 10) for 16 wk. Furthermore, essential mechanisms of IL-17A in atherogenesis were studied in vitro. Inhibition of IL-17A markedly prevented atherosclerotic lesion progression (p = 0.001) by reducing inflammatory burden and cellular infiltration (p = 0.01) and improved lesion stability (p = 0.01). In vitro experiments showed that IL-17A plays a role in chemoattractance, monocyte adhesion, and sensitization of APCs toward pathogen-derived TLR4 ligands. Also, IL-17A induced a unique transcriptome pattern in monocyte-derived macrophages distinct from known macrophage types. Stimulation of human carotid plaque tissue ex vivo with IL-17A induced a proinflammatory milieu and upregulation of molecules expressed by the IL-17A–induced macrophage subtype. In this study, we show that functional blockade of IL-17A prevents atherosclerotic lesion progression and induces plaque stabilization in advanced lesions in apolipoprotein E–deficient mice. The underlying mechanisms involve reduced inflammation and distinct effects of IL-17A on monocyte/macrophage lineage. In addition, translational experiments underline the relevance for the human system.

Beneficial effect of omega-3 fatty acids on sirolimus- or everolimus-induced hypertriglyceridemia in heart transplant recipients.

Background. Hyperlipidemia is an important complication after organ transplantation and may contribute to the development of posttransplant-accelerated coronary artery disease. Immunosuppressive therapy, especially mammalian target of rapamycin inhibitors, induces a considerable increase in cholesterol and triglyceride plasma levels. Omega-3 fatty acids (FAs) exert cardioprotective effects supporting a therapeutic role in cardiovascular conditions. Methods. An observational study of omega-3 FAs 4 g/day was performed in 15 heart transplant recipients with hypertriglyceridemia. Six patients received rapamycin, and nine received everolimus. Apart from one patient the immunosuppressive therapy was combined with mycophenolate mofetil, only one patient received steroids; two patients presented with diabetes. Results. Mean triglyceride levels before heart transplantation (HTx) were 137±54 mg/dL. After HTx, before sirolimus or everolimus treatment triglyceride level had increased to 188±67 mg/dL (P<0.05). Treatment with sirolimus or everolimus induced an increase in triglycerides to 354±107 mg/dL (P<0.001). Subsequent treatment with omega-3 FAs for 4 months resulted in a marked decrease in triglycerides to 226±74 mg/dL (P<0.001). All patients (100%) showed a reduction in triglyceride by more than 20% (responders). In 10 of 15 patients available 12-month data confirmed the long-term efficacy of omega-3 FAs treatment. There were no adverse events or any discontinuations; no changes in immunosuppression were required. Conclusions. Treatment with mammalian target of rapamycin inhibitors after HTx induces marked increase in serum levels of triglycerides. Omega-3 FAs significantly lower triglyceride levels and seem to be effective, safe, and well-tolerated in sirolimus- or everolimus-treated heart transplant recipients.

CXCL4-induced plaque macrophages can be specifically identified by co-expression of MMP7+S100A8+in vitro and in vivo

Macrophage heterogeneity in human atherosclerotic plaques has been recognized; however, markers for unequivocal identification of some subtypes are lacking. We found that the platelet chemokine CXCL4 induces a unique macrophage phenotype, which we proposed to call ‘M4’. Here, we sought to identify suitable markers that identify M4 macrophages in vitro and in vivo. Using a stringent algorithm, we identified a set of potential markers from transcriptomic data derived from polarized macrophages. We specifically focused on matrix metalloproteinase (MMP)7 and S100A8, the co-expression of which has not been described in any macrophage type thus far. We found dose- and time-dependent MMP7 and S100A8 expression in M4 macrophages at the gene and protein levels. CXCL4-induced up-regulation of both MMP7 and S100A8 was curbed in the presence of heparin, which binds to CXCL4 and glycosaminoglycans, most likely representing the macrophage receptor for CXCL4. Immunofluorescence of post-mortem atherosclerotic coronary arteries identified CD68+MMP7+, CD68+MMP7−, CD68+S100A8+ and CD68+S100A8− macrophages. A small proportion of MMP7+S100A8+ macrophages most likely represent M4 macrophages. In summary, we have identified co-expression of MMP7 and S100A8 to be a marker combination exclusively found in M4 macrophages. This finding may allow further dissection of the role of M4 macrophages in atherosclerosis and other pathologic conditions.

Effects of CTGF Blockade on Attenuation and Reversal of Radiation-Induced Pulmonary Fibrosis

Background: Radiotherapy is a mainstay for the treatment of lung cancer that can induce pneumonitis or pulmonary fibrosis. The matricellular protein connective tissue growth factor (CTGF) is a central mediator of tissue remodeling. Methods: A radiation-induced mouse model of pulmonary fibrosis was used to determine if transient administration of a human antibody to CTGF (FG-3019) started at different times before or after 20 Gy thoracic irradiation reduced acute and chronic radiation toxicity. Mice (25 mice/group; 10 mice/group in a confirmation study) were examined by computed tomography, histology, gene expression changes, and for survival. In vitro experiments were performed to directly study the interaction of CTGF blockade and radiation. All statistical tests were two-sided. Results: Administration of FG-3019 prevented (∼50%–80%) or reversed (∼50%) lung remodeling, improved lung function, improved mouse health, and rescued mice from lethal irradiation (P < .01). Importantly, when antibody treatment was initiated at 16 weeks after thoracic irradiation, FG-3019 reversed established lung remodeling and restored lung function. CTGF blockade abrogated M2 polarized macrophage influx, normalized radiation-induced gene expression changes, and reduced myofibroblast abundance and Osteopontin expression. Conclusion: These results indicate that blocking CTGF attenuates radiation-induced pulmonary remodeling and can reverse the process after initiation. CTGF has a central role in radiation-induced fibrogenesis, and FG-3019 may benefit patients with radiation-induced pulmonary fibrosis or patients with other forms or origin of chronic fibrotic diseases.

Reversible left ventricular dysfunction resembling Takotsubo syndrome after self-injection of adrenaline

Transient left ventricular (LV) ballooning syndrome, or Takotsubo syndrome, is characterized by a reversible LV dysfunction. The pathophysiology has not been fully elucidated, but an excess of catecholamines seems to have an essential role. The case of a 27-year-old man who developed transient LV dysfunction resembling Takotsubo syndrome after self-injection of adrenaline is described. The present case may provide additional evidence to the hypothesis of excess sympathetic activation in LV ballooning syndrome.

Inflammatory therapeutic targets in coronary atherosclerosis—from molecular biology to clinical application

Atherosclerosis is the leading cause of death worldwide. Over the past two decades, it has been clearly recognized that atherosclerosis is an inflammatory disease of the arterial wall. Accumulating data from animal experiments have supported this hypothesis, however, clinical applications making use of this knowledge remain scarce. In spite of optimal interventional and medical therapy, the risk for recurrent myocardial infarction remains by about 20% over 3 years after acute coronary syndromes, novel therapies to prevent atherogenesis or treat atherosclerosis are urgently needed. This review summarizes selected potential molecular inflammatory targets that may be of clinical relevance. We also review recent and ongoing clinical trails that target inflammatory processes aiming at preventing adverse cardiovascular events. Overall, it seems surprising that translation of basic science into clinical practice has not been a great success. In conclusion, we propose to focus on specific efforts that promote translational science in order to improve outcome and prognosis of patients suffering from atherosclerosis.

Increased adherence eight months after switch from twice daily calcineurin inhibitor based treatment to once daily modified released tacrolimus in heart transplantation

Background Modified-release tacrolimus (TAC) is a new, once-daily oral formulation of the established immunosuppressive agent TAC. This study evaluated long-term patient adherence, as well as safety and efficacy, in stable patients after heart transplantation (HTx) who switched from a conventional twice daily calcineurin inhibitor-based regimen (TAC or cyclosporine A [CsA]) to a once-daily modified-release TAC regimen. Methods Stable patients were switched from conventional TAC or CsA (twice-daily dosing) to modified-release TAC (once-daily dosing) according to manufacturer’s recommendations using a pre-experimental design. Self-reported adherence was assessed at baseline and 8 months after the switch with the Basel Assessment of Adherence with Immunosuppressive Medication Scale (BAASIS). Additionally, routine laboratory values were analyzed 8 months after switch. Results Of 76 patients (58 male, 18 female) initially included, 72 were available for statistical analysis, as modified-release TAC was discontinued due to diarrhea in one patient and gastrointestinal discomfort in three patients. Overall nonadherence at baseline for any of the four BAASIS items was 75.0% versus 40.3% after 8 months (P<0.0001). After 8 months, adherence was improved in 41 patients (56.9%), unchanged in 27 (37.5%), and reduced in four patients (5.6%). The BAASIS visual analog scale score improved significantly from 87.0% ± 13.5% to 97.5% ± 5.7% (P<0.0001). No significant changes were observed for hematological, renal, or liver function parameters after 8 months (all P=not significant). Conclusion To our knowledge, this is the first study in stable patients after HTx to demonstrate a significant improvement in long-term (ie, 8-month) patient adherence after the switch to modified-release TAC. Modified-release TAC was generally well tolerated. Further studies are currently underway to investigate long-term safety after HTx of various calcineurin inhibitors for prevention of rejection and occurrence of side effects.