Atherosclerotic plaque localization correlates with regions of disturbed flow in which endothelial cells (ECs) align poorly, whereas sustained laminar flow correlates with cell alignment in the direction of flow and resistance to atherosclerosis. We now report that in hypercholesterolemic mice, deletion of syndecan 4 (S4 −/− ) drastically increased atherosclerotic plaque burden with the appearance of plaque in normally resistant locations. Strikingly, ECs from the thoracic aortas of S4 −/− mice were poorly aligned in the direction of the flow. Depletion of S4 in human umbilical vein endothelial cells (HUVECs) using shRNA also inhibited flow-induced alignment in vitro, which was rescued by re-expression of S4. This effect was highly specific, as flow activation of VEGF receptor 2 and NF-κB was normal. S4-depleted ECs aligned in cyclic stretch and even elongated under flow, although nondirectionally. EC alignment was previously found to have a causal role in modulating activation of inflammatory versus antiinflammatory pathways by flow. Consistent with these results, S4-depleted HUVECs in long-term laminar flow showed increased activation of proinflammatory NF-κB and decreased induction of antiinflammatory kruppel-like factor (KLF) 2 and KLF4. Thus, S4 plays a critical role in sensing flow direction to promote cell alignment and inhibit atherosclerosis. mechanotransduction | polarity | shear stress | atherosclerosis S yndecan 4 (S4) is a transmembrane heparan sulfate proteoglycan that serves as a coreceptor for extracellular matrix proteins and growth factors (1-3). S4−/− mice are viable and fertile (4, 5) but show defective wound healing consequent to impaired angiogenesis (6). They also have higher mortality after LPS injection (7) and exhibit defective muscle repair and myofiber organization as a result of inefficient differentiation and migration of muscle satellite cells (8). We and others have also demonstrated that S4 plays a critical role in the control of cell polarity, by controlling Rho GTPase activity (9-11), as well as in planar cell polarity (12). S4 has also been recently identified as a putative mechanosensor (13).Atherosclerosis is an inflammatory disease of large to midsized arteries that is the major cause of illness and death in developed nations and is rapidly increasing in developing nations (14,15). It is linked to a variety of risk factors including high LDL cholesterol level and triglycerides, diabetes, smoking, hypertension, sedentary lifestyle, and inflammatory mediators. However, atherosclerotic lesions occur selectively in regions of arteries that are subject to disturbances in fluid shear stress (FSS), the frictional force flowing blood exerts on the endothelium. Regions of arteries with lower flow magnitude, flow reversal, and other complex spatial/ temporal flow patterns are predisposed to atherosclerosis. Systemic risk factors appear to synergize with local biomechanical factors in the initiation and progression of atherosclerotic lesions (16).The importance of S4 in endothelial bi...

Background-Renin released by ischemia/reperfusion from cardiac mast cells activates a local renin-angiotensin system (RAS). This exacerbates norepinephrine release and reperfusion arrhythmias (ventricular tachycardia and fibrillation), making RAS a new therapeutic target in myocardial ischemia. Methods and Results-We investigated whether ischemic preconditioning (IPC) prevents cardiac RAS activation in guinea pig hearts ex vivo. When ischemia/reperfusion (20 minutes of ischemia/30 minutes of reperfusion) was preceded by IPC (two 5-minute ischemia/reperfusion cycles), renin and norepinephrine release and ventricular tachycardia and fibrillation duration were markedly decreased, a cardioprotective anti-RAS effect. Activation and blockade of adenosine A 2b /A 3 receptors and activation and inhibition of protein kinase C⑀ (PKC⑀) mimicked and prevented, respectively, the anti-RAS effects of IPC. Moreover, activation of A 2b /A 3 receptors or activation of PKC⑀ prevented degranulation and renin release elicited by peroxide in cultured mast cells (HMC-1). Activation and inhibition of mitochondrial aldehyde dehydrogenase type-2 (ALDH2) also mimicked and prevented, respectively, the cardioprotective anti-RAS effects of IPC. Furthermore, ALDH2 activation inhibited degranulation and renin release by reactive aldehydes in HMC-1. Notably, PKC⑀ and ALDH2 were both activated by A 2b /A 3 receptor stimulation in HMC-1, and PKC⑀ inhibition prevented ALDH2 activation. Conclusions-The

We found that synthetic peptides in the form of dendrimers become resistant to proteolysis. To determine the molecular basis of this resistance, different bioactive peptides were synthesized in monomeric, two-branched and tetra-branched form and incubated with human plasma and serum. Proteolytic resistance of branched multimeric sequences was compared to that of the same peptides synthesized as multimeric linear molecules. Unmodified peptides and cleaved sequences were detected by high pressure liquid chromatography and mass spectrometry. An increase in peptide copies did not increase peptide resistance in linear multimeric sequences, whereas multimericity progressively enhanced proteolytic stability of branched multimeric peptides. A structure-based hypothesis of branched peptide resistance to proteolysis by metallopeptidases is presented.

The contribution of endothelial-derived miR-17∼92 to ischemiainduced arteriogenesis has not been investigated in an in vivo model. In the present study, we demonstrate a critical role for the endothelial-derived miR-17∼92 cluster in shaping physiological and ischemiatriggered arteriogenesis. Endothelial-specific deletion of miR-17∼92 results in an increase in collateral density limbs and hearts and in ischemic limbs compared with control mice, and consequently improves blood flow recovery. Individual cluster components positively or negatively regulate endothelial cell (EC) functions in vitro, and, remarkably, ECs lacking the cluster spontaneously form cords in a manner rescued by miR-17a, -18a, and -19a. Using both in vitro and in vivo analyses, we identified FZD4 and LRP6 as targets of miR-19a/b. Both of these targets were up-regulated in 17∼92 KO ECs compared with control ECs, and both were shown to be targeted by miR-19 using luciferase assays. We demonstrate that miR-19a negatively regulates FZD4, its coreceptor LRP6, and WNT signaling, and that antagonism of miR-19a/b in aged mice improves blood flow recovery after ischemia and reduces repression of these targets. Collectively, these data provide insights into miRNA regulation of arterialization and highlight the importance of vascular WNT signaling in maintaining arterial blood flow.endothelium | arteriogenesis | vascular | microRNA