The intermediate filament (IF) cytoskeleton has been proposed to regulate morphogenic processes by integrating the cell fate signaling machinery with mechanical cues. Signaling between endothelial cells (ECs) and vascular smooth muscle cells (VSMCs) through the Notch pathway regulates arterial remodeling in response to changes in blood flow. Here we show that the IF-protein vimentin regulates Notch signaling strength and arterial remodeling in response to hemodynamic forces. Vimentin is important for Notch transactivation by ECs and vimentin knockout mice (VimKO) display disrupted VSMC differentiation and adverse remodeling in aortic explants and in vivo . Shear stress increases Jagged1 levels and Notch activation in a vimentin-dependent manner. Shear stress induces phosphorylation of vimentin at serine 38 and phosphorylated vimentin interacts with Jagged1 and increases Notch activation potential. Reduced Jagged1-Notch transactivation strength disrupts lateral signal induction through the arterial wall leading to adverse remodeling. Taken together we demonstrate that vimentin forms a central part of a mechanochemical transduction pathway that regulates multilayer communication and structural homeostasis of the arterial wall.

Traditionally, multiple sclerosis (MS) has been considered a white matter disease with focal inflammatory lesions. It is, however, becoming clear that significant pathology, such as microglial activation, also takes place outside the plaque areas, that is, in areas of normal-appearing white matter (NAWM) and gray matter (GM). Microglial activation can be detected in vivo using 18-kDa translocator protein (TSPO)-binding radioligands and PET. It is unknown whether fingolimod affects microglial activation in MS. The aim of this study was to investigate whether serial PET can be used to evaluate the effect of fingolimod treatment on microglial activation. Ten relapsing-remitting MS patients were studied using the TSPO radioligandC-()-PK11195. Imaging was performed at baseline and after 8 and 24 wk of fingolimod treatment. Eight healthy individuals were imaged for comparison. Microglial activation was evaluated as distribution volume ratio of C-()-PK11195. The patients had MS for an average of 7.9 ± 4.3 y (mean ± SD), their total relapses averaged 4 ± 2.4, and their Expanded Disability Status Scale was 2.7 ± 0.5. The patients were switched to fingolimod because of safety reasons or therapy escalation. The mean washout period before the initiation of fingolimod was 2.3 ± 1.1 mo. The patients were clinically stable on fingolimod. At baseline, microglial activation was significantly higher in the combined NAWM and GM areas of MS patients than in healthy controls ( 0.021). C-()-PK11195 binding was reduced (-12.31%) within the combined T2 lesion area after 6 mo of fingolimod treatment ( 0.040) but not in the areas of NAWM or GM. Fingolimod treatment reduced microglial/macrophage activation at the site of focal inflammatory lesions, presumably by preventing leukocyte trafficking from the periphery. It did not affect the widespread, diffuse microglial activation in the NAWM and GM. The study opens new vistas for designing future therapeutic studies in MS that use the evaluation of microglial activation as an imaging outcome measure.

Background The melanocortin 1 receptor (MC1-R) is expressed by monocytes and macrophages, where it exerts anti-inflammatory actions upon stimulation with its natural ligand α-melanocyte-stimulating hormone (α-MSH). The present study was designed to investigate the specific role of MC1-R in the context of atherosclerosis and possible regulatory pathways of MC1-R beyond anti-inflammation. Methods Human and mouse atherosclerotic samples and primary mouse macrophages were used to study the regulatory functions of MC1-R. The impact of pharmacological MC1-R activation on atherosclerosis was assessed in apolipoprotein E deficient (ApoE−/−) mice. Results Characterization of human and mouse atherosclerotic plaques revealed that MC1-R expression localizes in lesional macrophages and is significantly associated with the ATP-binding cassette transporters ABCA1 and ABCG1, which are responsible for initiating reverse cholesterol transport. Using bone marrow-derived macrophages, we observed that α-MSH and selective MC1-R agonists similarly promoted cholesterol efflux, which is a counter-regulatory mechanism against foam cell formation. Mechanistically, MC1-R activation upregulated the levels of ABCA1 and ABCG1. These effects were accompanied by a reduction in cell surface CD36 expression and in cholesterol uptake, further protecting macrophages from excessive lipid accumulation. Conversely, macrophages deficient in functional MC1-R displayed a phenotype with impaired efflux and enhanced uptake of cholesterol. Pharmacological targeting of MC1-R in atherosclerotic ApoE−/− mice reduced plasma cholesterol levels and aortic CD36 expression as well as increased plaque ABCG1 expression and signs of plaque stability. Conclusions Our findings identify a novel role for MC1-R in macrophage cholesterol transport. Activation of MC1-R confers protection against macrophage foam cell formation through a dual mechanism: it prevents cholesterol uptake while concomitantly promoting ABCA1- and ABCG1-mediated reverse cholesterol transport.

A therosclerosis is a chronic inflammatory disease causing progressive lesion formation and luminal narrowing of arteries. The underlying pathology is initiated by endothelial dysfunction and structural alterations after an imbalanced lipid metabolism and trapping of low-density lipoprotein (LDL) particles in the intima of arteries.1,2 Subsequently, intimal lipid accumulation triggers the release of various chemokines by activated endothelial cells, inducing a multiphase cascade of leukocyte infiltration and inflammatory responses in the arterial walls. As the knowledge of these inflammatory pathways has been growing during the past years, it has also uncovered new druggable targets that could complement the current treatment options, which do not directly interfere with the central inflammatory mechanisms driving atheroprogression. One endogenous pathway that has gained increasing attention for its wide-ranging and potent actions in suppressing maladaptive inflammatory responses is the melanocortin system consisting of melanocortin peptides and their cellular receptors. 3,4 However, the role of melanocortin signaling and its promise as a therapeutic target in atherosclerosis remain fully unexplored.Melanocortins are a family of peptides that are proteolytically cleaved from the common precursor molecule pro-opiomelanocortin. These peptides include melanocyte-stimulating hormones (α-, β-, and γ-MSH) and adrenocorticotropic hormone. They regulate important physiological functions by acting via G-protein-coupled melanocortin receptors (MC-Rs), named from MC1-R to MC5-R. 5,6 Our recent findings indicate that α-MSH serves as a protective regulator in the vasculature by enhancing endothelium-dependent control of blood vessel tone. 7 Mechanistically, α-MSH was shown to augment vascular nitric oxide (NO) availability by activating MC1-R in the endothelium. Besides promoting endothelial function, mounting evidence indicates that α-MSH, through the activation of © 2014 American Heart Association, Inc. Objective-Melanocortin peptides have been shown to elicit anti-inflammatory actions and to promote vascular endothelial function by activating type 1 and 3 melanocortin receptors. Here, we addressed whether these favorable properties of melanocortins could reduce atherosclerotic plaque inflammation and improve vasoreactivity in atherosclerotic mice. Approach and Results-Low-density lipoprotein receptor-deficient mice expressing only apolipoprotein B100 were fed a high-fat diet for 8 or 16 weeks and treated with either vehicle or a stable melanocortin analog, melanotan II (MT-II, 0.3 mg/kg per day, 4 weeks). We determined plaque uptake of fluorine-18-labeled fluorodeoxyglucose as a surrogate marker for atherosclerotic plaque inflammation and vascular function of the aorta by ex vivo analyses. MT-II had no effect on body weight or composition, or plasma cholesterol levels in atherosclerotic mice. Without attenuating atherosclerotic lesion size or lesional macrophage accumulation, MT-II treatment reduced fluorine-18-labeled...