Jan H. von der Thüsen

Interleukins in Atherosclerosis: Molecular Pathways and Therapeutic Potential

Interleukins are considered to be key players in the chronic vascular inflammatory response that is typical of atherosclerosis. Thus, the expression of proinflammatory interleukins and their receptors has been demonstrated in atheromatous tissue, and the serum levels of several of these cytokines have been found to be positively correlated with (coronary) arterial disease and its sequelae. In vitro studies have confirmed the involvement of various interleukins in pro-atherogenic processes, such as the up-regulation of adhesion molecules on endothelial cells, the activation of macrophages, and smooth muscle cell proliferation. Furthermore, studies in mice deficient or transgenic for specific interleukins have demonstrated that, whereas some interleukins are indeed intrinsically pro-atherogenic, others may have anti-atherogenic qualities. As the roles of individual interleukins in atherosclerosis are being uncovered, novel anti-atherogenic therapies, aimed at the modulation of interleukin function, are being explored. Several approaches have produced promising results in this respect, including the transfer of anti-inflammatory interleukins and the administration of decoys and antibodies directed against proinflammatory interleukins. The chronic nature of the disease and the generally pleiotropic effects of interleukins, however, will demand high specificity of action and/or effective targeting to prevent the emergence of adverse side effects with such treatments. This may prove to be the real challenge for the development of interleukin-based anti-atherosclerotic therapies, once the mediators and their targets have been delineated.

Induction of Rapid Atherogenesis by Perivascular Carotid Collar Placement in Apolipoprotein E–Deficient and Low-Density Lipoprotein Receptor–Deficient Mice

Background —Perivascular collar placement has been used as a means for localized atherosclerosis induction in a variety of experimental animal species. In mice, however, atherosclerosis-like lesions have thus far not been obtained by this method. The aim of this study was the development of a mouse model of rapid, site-controlled atherogenesis. Methods and Results —Silastic collars were placed around the carotid arteries of apolipoprotein E–deficient (apoE−/−) and LDL receptor–deficient (LDLr−/−) mice. The development of collar-induced lesions was found to occur predominantly in the area proximal to the collar and to be dependent on a high-cholesterol diet. Lesions were evident in apoE−/− mice after 3 weeks and in LDLr−/− mice after 6 weeks and were overtly atherosclerotic in appearance. Lumen stenosis reached 85% in apoE−/− mice and 61% in LDLr−/− mice 6 weeks after collar insertion. Expression levels of intercellular adhesion molecule-1 and vascular cell adhesion molecule-1 were increased both proximal and distal to the collar, whereas endothelial nitric oxide synthase expression was downregulated at the proximal site. Conclusions —We propose that this model of collar-induced acceleration of carotid atherogenesis is of hemodynamic cause. It may serve as a substrate for sequential mechanistic studies concerned with the underlying cause and pathogenesis of atherosclerosis. The rapidity of lesion development will also aid the efficient screening of new potentially antiatherogenic chemical entities and the evaluation of therapies with limited duration of effectiveness, such as adenoviral gene therapy.

Induction of atherosclerotic plaque rupture in apolipoprotein E-/- mice after adenovirus-mediated transfer of p53

Background—The presence of the tumor-suppressor gene p53 in advanced atherosclerotic plaques and the sensitivity to p53-induced cell death of smooth muscle cells isolated from these plaques have fueled speculation about the role of p53 in lesion destabilization and plaque rupture. In this study, we describe a strategy to promote (thrombotic) rupture of preexisting atherosclerotic lesions using p53-induced lesion remodeling. Methods and Results—Carotid atherogenesis was initiated in apolipoprotein E knockout mice by placement of a perivascular silastic collar. The resulting plaques were incubated transluminally with recombinant adenovirus carrying either a p53 or &bgr;-galactosidase (lacZ) transgene. p53 transfection was restricted to the smooth muscle cell-rich cap of the plaque and led to an increase in cap cell apoptosis 1 day after transfer. p53 overexpression resulted in a marked decrease in the cellular and extracellular content of the cap, reflected by a markedly reduced cap/intima ratio (0.21±0.04 versus 0.46±0.03, P <0.001). The latter is a characteristic feature of plaque vulnerability to rupture, and whereas spontaneous rupture of p53-treated lesions was rare, it was found in 40% of cases after treatment with the vasopressor compound phenylephrine (P =0.003). Conclusions—We have demonstrated a potential role of p53-induced remodeling in atherosclerotic plaque destabilization. Being the first example of inducible rupture at a predefined location, this model offers a unique opportunity to delineate the processes that precede rupture and to evaluate plaque-stabilizing therapies.

Short Communication: The Neuropeptide Substance P Mediates Adventitial Mast Cell Activation and Induces Intraplaque Hemorrhage in Advanced Atherosclerosis

Rationale: Although we and others have recently shown that mast cells play an important role in plaque progression and destabilization, the nature of the actual trigger for (peri)vascular mast cell activation during atherosclerosis is still unresolved. Objective: In this study, we confirm that perivascular mast cell content correlates with the number of nerve fibers in the adventitia of human coronary atherosclerotic plaque specimen. Because peripheral C-type nerve fibers secrete, among others, substance P, a potent mast cell activator, we set out to study effects of adventitial administration of this neuropeptide on mast cell dependent destabilization of carotid artery plaques in apolipoprotein E–deficient (apoE−/−) mice. Methods and Results: Substance P treatment significantly enhanced the number and activation status of adventitial mast cells compared to controls and promoted intraplaque hemorrhages. These phenomena could be prevented by coadministration of the neurokinin-1 receptor antagonist spantide I and did not occur in mast cell deficient apoE−/− mice, establishing the critical involvement of mast cells in substance P–elicited plaque destabilization. Conclusions: Our data suggest that neurotransmitters such as substance P are capable of promoting mast cell dependent plaque destabilization and provide a new, direct link between neural factors and vascular inflammation.

Serine Protease Inhibitor Serp-1 Strongly Impairs Atherosclerotic Lesion Formation and Induces a Stable Plaque Phenotype in ApoE−/− Mice

Abstract— The myxoma virus protein Serp-1 is a member of the serine protease inhibitor superfamily. Serp-1 potently inhibits human serum proteases including plasmin, urokinase-type plasminogen activator (uPA), and tissue-type plasminogen activator (tPA). Serp-1 also displays a high antiinflammatory activity, rendering it a promising candidate for antiatherosclerotic therapy. In this study, we have thus examined the effect of Serp-1 on de novo atherosclerotic plaque formation and on advanced lesions. Perivascular collars were placed around carotid arteries of ApoE−/− mice to induce atherosclerotic plaques and Serp-1 treatment started at week 1 and week 5 after collar placement. Effects of Serp-1 on de novo atherogenesis were characterized by a significantly lower plaque size than that of control mice (18±5×103 versus 57±12×103 &mgr;m2, respectively; P =0.007). Immunostaining showed a 50% (P =0.004) decrease in the MOMA-2–stained lesion area of Serp-1–treated mice. Treatment of advanced lesions with Serp-1 resulted in a decrease in plaque size and lumen stenosis (P =0.028). &agr;-Actin staining of these lesions was significantly increased compared with the control (P =0.017). In both studies, a higher cellularity of the plaque and increased collagen content was observed in Serp-1–treated mice. In vitro studies showed that Serp-1 induces proliferation and migration of vascular smooth muscle cells. In conclusion, Serp-1 inhibits carotid artery plaque growth and progression in ApoE−/− mice. Equally relevant, it enhances cellularity of the plaque core potentially leading to improved plaque stability. The above results indicate that Serp-1 constitutes a promising lead in antiatherosclerotic therapy.

Membrane-anchored Serine Protease Matriptase Is a Trigger of Pulmonary Fibrogenesis

RATIONALE Idiopathic pulmonary fibrosis (IPF) is a devastating disease that remains refractory to current therapies. OBJECTIVES To characterize the expression and activity of the membrane-anchored serine protease matriptase in IPF in humans and unravel its potential role in human and experimental pulmonary fibrogenesis. METHODS Matriptase expression was assessed in tissue specimens from patients with IPF versus control subjects using quantitative reverse transcriptase-polymerase chain reaction, immunohistochemistry, and Western blotting, while matriptase activity was monitored by fluorogenic substrate cleavage. Matriptase-induced fibroproliferative responses and the receptor involved were characterized in human primary pulmonary fibroblasts by Western blot, viability, and migration assays. In the murine model of bleomycin-induced pulmonary fibrosis, the consequences of matriptase depletion, either by using the pharmacological inhibitor camostat mesilate (CM), or by genetic down-regulation using matriptase hypomorphic mice, were characterized by quantification of secreted collagen and immunostainings. MEASUREMENTS AND MAIN RESULTS Matriptase expression and activity were up-regulated in IPF and bleomycin-induced pulmonary fibrosis. In cultured human pulmonary fibroblasts, matriptase expression was significantly induced by transforming growth factor-β. Furthermore, matriptase elicited signaling via protease-activated receptor-2 (PAR-2), and promoted fibroblast activation, proliferation, and migration. In the experimental bleomycin model, matriptase depletion, by the pharmacological inhibitor CM or by genetic down-regulation, diminished lung injury, collagen production, and transforming growth factor-β expression and signaling. CONCLUSIONS These results implicate increased matriptase expression and activity in the pathogenesis of pulmonary fibrosis in human IPF and in an experimental mouse model. Overall, targeting matriptase, or treatment by CM, which is already in clinical use for other diseases, may represent potential therapies for IPF.

In vivo imaging of the airway wall in asthma: fibered confocal fluorescence microscopy in relation to histology and lung function.

BackgroundAirway remodelling is a feature of asthma including fragmentation of elastic fibres observed in the superficial elastin network of the airway wall. Fibered confocal fluorescence microscopy (FCFM) is a new and non-invasive imaging technique performed during bronchoscopy that may visualize elastic fibres, as shown by in vitro spectral analysis of elastin powder. We hypothesized that FCFM images capture in vivo elastic fibre patterns within the airway wall and that such patterns correspond with airway histology. We aimed to establish the concordance between the bronchial elastic fibre pattern in histology and FCFM. Second, we examined whether elastic fibre patterns in histology and FCFM were different between asthmatic subjects and healthy controls. Finally, the association between these patterns and lung function parameters was investigated.MethodsIn a cross-sectional study comprising 16 subjects (8 atopic asthmatic patients with controlled disease and 8 healthy controls) spirometry and bronchoscopy were performed, with recording of FCFM images followed by endobronchial biopsy at the airway main carina. Elastic fibre patterns in histological sections and FCFM images were scored semi-quantitatively. Agreement between histology and FCFM was analysed using linearly weighted kappa κw.ResultsThe patterns observed in histological sections and FCFM images could be divided into 3 distinct groups. There was good agreement between elastic fibre patterns in histology and FCFM patterns (κw 0.744). The semi-quantitative pattern scores were not different between asthmatic patients and controls. Notably, there was a significant difference in post-bronchodilator FEV1 %predicted between the different patterns by histology (p = 0.001) and FCFM (p = 0.048), regardless of asthma or atopy.ConclusionFCFM captures the elastic fibre pattern within the airway wall in humans in vivo. The association between post-bronchodilator FEV1 %predicted and both histological and FCFM elastic fibre patterns points towards a structure-function relationship between extracellular matrix in the airway wall and lung function.Trial registrationNetherlands Trial Register NTR1306

A Randomized Controlled Clinical Trial Comparing Belatacept With Tacrolimus After De Novo Kidney Transplantation

Background Belatacept, an inhibitor of the CD28-CD80/86 costimulatory pathway, allows for calcineurin-inhibitor free immunosuppressive therapy in kidney transplantation but is associated with a higher acute rejection risk than ciclosporin. Thus far, no biomarker for belatacept-resistant rejection has been validated. In this randomized-controlled trial, acute rejection rate was compared between belatacept- and tacrolimus-treated patients and immunological biomarkers for acute rejection were investigated. Methods Forty kidney transplant recipients were 1:1 randomized to belatacept or tacrolimus combined with basiliximab, mycophenolate mofetil, and prednisolone. The 1-year incidence of biopsy-proven acute rejection was monitored. Potential biomarkers, namely, CD8+CD28−, CD4+CD57+PD1−, and CD8+CD28++ end-stage terminally differentiated memory T cells were measured pretransplantation and posttransplantation and correlated to rejection. Pharmacodynamic monitoring of belatacept was performed by measuring free CD86 on monocytes. Results The rejection incidence was higher in belatacept-treated than tacrolimus-treated patients: 55% versus 10% (P = 0.006). All 3 graft losses, due to rejection, occurred in the belatacept group. Although 4 of 5 belatacept-treated patients with greater than 35 cells CD8+CD28++ end-stage terminally differentiated memory T cells/&mgr;L rejected, median pretransplant values of the biomarkers did not differ between belatacept-treated rejectors and nonrejectors. In univariable Cox regressions, the studied cell subsets were not associated with rejection-risk. CD86 molecules on circulating monocytes in belatacept-treated patients were saturated at all timepoints. Conclusions Belatacept-based immunosuppressive therapy resulted in higher and more severe acute rejection compared with tacrolimus-based therapy. This trial did not identify cellular biomarkers predictive of rejection. In addition, the CD28-CD80/86 costimulatory pathway appeared to be sufficiently blocked by belatacept and did not predict rejection.

High endogenous activated protein C levels attenuates bleomycin-induced pulmonary fibrosis

Coagulation activation accompanied by reduced anticoagulant activity is a key characteristic of patients with idiopathic pulmonary fibrosis (IPF). Although the importance of coagulation activation in IPF is well studied, the potential relevance of endogenous anticoagulant activity in IPF progression remains elusive. We assess the importance of the endogenous anticoagulant protein C pathway on disease progression during bleomycin‐induced pulmonary fibrosis. Wild‐type mice and mice with high endogenous activated protein C APC levels (APChigh) were subjected to bleomycin‐induced pulmonary fibrosis. Fibrosis was assesses by hydroxyproline and histochemical analysis. Macrophage recruitment was assessed immunohistochemically. In vitro, macrophage migration was analysed by transwell migration assays. Fourteen days after bleomycin instillation, APChigh mice developed pulmonary fibrosis to a similar degree as wild‐type mice. Interestingly, Aschcroft scores as well as lung hydroxyproline levels were significantly lower in APChigh mice than in wild‐type mice on day 28. The reduction in fibrosis in APChigh mice was accompanied by reduced macrophage numbers in their lungs and subsequent in vitro experiments showed that APC inhibits thrombin‐dependent macrophage migration. Our data suggest that high endogenous APC levels inhibit the progression of bleomycin‐induced pulmonary fibrosis and that APC modifies pulmonary fibrosis by limiting thrombin‐dependent macrophage recruitment.

Transcatheter Lotus Valve Implantation in a Stenotic Mitral Valve

A 75-year-old woman with degenerative mitral stenosis and a prior aortic bioprosthesis was referred for potential valvular intervention. She had been symptomatic (New York Heart Association functional classes III to IV), with a history of syncope, chronic obstructive pulmonary disease, latent