Background-Monocyte activation and migration into the arterial wall are key events in atherogenesis associated with hypercholesterolemia. CD11c/CD18, a ␤ 2 integrin expressed on human monocytes and a subset of mouse monocytes, has been shown to play a distinct role in human monocyte adhesion on endothelial cells, but the regulation of CD11c in hypercholesterolemia and its role in atherogenesis are unknown. Methods and Results-Mice genetically deficient in CD11c were generated and crossbred with apolipoprotein E (apoE) Ϫ/Ϫ mice to generate CD11c Ϫ/Ϫ /apoE Ϫ/Ϫ mice. Using flow cytometry, we examined CD11c on blood leukocytes in apoE Ϫ/Ϫ hypercholesterolemic mice and found that compared with wild-type and apoE Ϫ/Ϫ mice on a normal diet, apoE Ϫ/Ϫ mice on a Western high-fat diet had increased CD11c ϩ monocytes. Circulating CD11c ϩ monocytes from apoE Ϫ/Ϫ mice fed a high-fat diet exhibited cytoplasmic lipid vacuoles and expressed higher levels of CD11b and CD29. Deficiency of CD11c decreased firm arrest of mouse monocytes on vascular cell adhesion molecule-1 and E-selectin in a shear flow assay, reduced monocyte/macrophage accumulation in atherosclerotic lesions, and decreased atherosclerosis development in apoE Ϫ/Ϫ mice on a high-fat diet. Conclusions-CD11c, which increases on blood monocytes during hypercholesterolemia, plays an important role in monocyte recruitment and atherosclerosis development in an apoE Ϫ/Ϫ mouse model of hypercholesterolemia. Key Words: atherosclerosis Ⅲ cell adhesion molecules Ⅲ leukocytes A therosclerosis associated with hypercholesterolemia is a complex inflammatory process, characterized pathologically by recruitment of monocytic leukocytes in the arterial wall and lipid accumulation in monocytic leukocytes. 1 Monocyte recruitment is a multistep process mediated by adhesion molecules, beginning with rolling, which is mediated by short-lived bonds between E-selectin on endothelial cells (ECs) and sialylated ligands such as P-selectin glycoprotein ligand-1 on monocytes, followed by firm arrest facilitated through interactions between activated ␤ 1 and ␤ 2 integrins on monocytes with vascular cell adhesion molecule-1 (VCAM-1) and intercellular adhesion molecule-1 (ICAM-1) on ECs. Firmly arrested monocytes subsequently undergo transmigration through other adhesion molecules. 2,3 Therefore, adhesion molecules participating in monocyte-EC interactions play a critical role in atherogenesis. 4 EC activation induced by hypercholesterolemia increases expression of VCAM-1, ICAM-1, and E-selectin, thereby contributing to atherogenesis. 4 -6 However, the effect of hypercholesterolemia on monocyte activation and its contribution to atherogenesis are less defined. Clinical Perspective on p 2717The ␤ 2 integrins, which include CD11a/CD18, CD11b/ CD18, CD11c/CD18, and CD11d/CD18, 7 contribute to atherogenesis as evidenced by a significant reduction in atherosclerosis development in CD18 Ϫ/Ϫ mice, which lack all 4 CD11/CD18 integrins. 4 CD11b has been used as an activation marker for monocytes/macrophages...

Breast cancer is a leading cause of death for women, with mortality resulting from metastasis. Metastases are often detected once tumor cells affect the function of solid organs, with a high disease burden limiting effective treatment. Here we report a method for the early detection of metastasis using an implanted scaffold to recruit and capture metastatic cells in vivo, which achieves high cell densities and reduces the tumor burden within solid organs 10-fold. Recruitment is associated with infiltration of immune cells, which include Gr1hiCD11b+ cells. We identify metastatic cells in the scaffold through a label-free detection system using inverse-spectroscopic optical coherence tomography, which identifies changes to nanoscale tissue architecture associated with the presence of tumor cells. For patients at risk of recurrence, scaffold implantation following completion of primary therapy has the potential to identify metastatic disease at the earliest stage, enabling initiation of therapy while the disease burden is low.

Objective Atherosclerosis is associated with monocyte adhesion to the arterial wall that involves integrin activation and emigration across inflamed endothelium. Involvement of β2-integrin CD11c/CD18 in atherogenesis was recently shown in dyslipidemic mice, which motivates our study of its inflammatory function during hypertriglyceridemia in humans. Methods and Results Flow cytometry of blood from healthy subjects fed a standardized high fat meal revealed that at 3.5 hours postprandial, monocyte CD11c surface expression was elevated and the extent of upregulation correlated with blood triglycerides. Monocytes from postprandial blood exhibited an increased light scatter profile, which correlated with elevated CD11c expression and uptake of lipid particles. Purified monocytes internalized triglyceride-rich lipoproteins isolated from postprandial blood through LRP-1, and this also elicited CD11c upregulation. Lab-on-a-chip analysis of whole blood showed that monocyte arrest on a VCAM-1 substrate under shear flow was elevated at 3.5 hours and correlated with blood triglyceride and CD11c expression. At 7 hours postprandial, blood triglycerides decreased and monocyte CD11c expression and arrest on VCAM-1 returned to fasting levels. Conclusions During hypertriglyceridemia, monocytes internalize lipid, upregulate CD11c, and increase adhesion to VCAM-1. These data suggest that analysis of monocyte inflammation may provide additional framework for evaluating individual susceptibility to cardiovascular disease.

Mac-1 dependent crawling is a new step in the leukocyte recruitment cascade which follows LFA-1 dependent adhesion and precedes emigration. Neutrophil adhesion via LFA-1 has been shown to induce cytoskeletal reorganization through Vav1-dependent signaling, and the current study investigates the role of Vav1 in the leukocyte recruitment process in vivo with particular attention to the events immediately downstream of LFA-1 dependent adhesion. Intravital and spinning-disk-confocal microscopy was used to investigate intravascular crawling in relation to endothelial junctions in vivo in wild-type (WT) and Vav1−/− mice. Adherent WT neutrophils almost immediately began crawling perpendicular to or against blood flow via Mac-1 until they reached an endothelial junction where they often changed direction. This pattern of perpendicular, mechanotactic crawling was recapitulated in vitro when shear was applied. In sharp contrast, the movement of Vav1−/− neutrophils was always in the direction of flow, and appeared more passive as if the cells were dragged in the direction of flow in vivo and in vitro. More than 80% of Vav1−/− neutrophils moved independent of Mac-1 and could be detached with LFA-1 antibodies. An inability to release the uropod was frequently noted for Vav1−/− neutrophils, leading to greatly elongated tails. The Vav1−/− neutrophils failed to stop or follow junctions, and ultimately detached leading to fewer emigrated neutrophils. The Vav1−/− phenotype resulted in fewer neutrophils recruited in a relevant model of infectious peritonitis. Clearly, Vav1 is critical for the complex interplay between LFA-1 and Mac-1 that underlies the programmed intravascular crawling of neutrophils.

Objective-Atherosclerosis is a focal disease that develops at sites of low and oscillatory shear stress in arteries. This study aimed to understand how endothelial cells sense a gradient of fluid shear stress and transduce signals that regulate membrane expression of cell adhesion molecules and monocyte recruitment.Methods-Human aortic endothelial cells were stimulated with TNF-α and simultaneously exposed to a linear gradient of shear stress that increased from 0 to 16 dyne/cm 2 . Cell adhesion molecule expression and activation of NFκB were quantified by immunofluorescence microscopy with resolution at the level of a single endothelial cell. Monocyte recruitment was imaged using custom microfluidic flow chambers.Results-VCAM-1 and E-selectin upregulation was greatest between 2-4 dyne/cm 2 (6 and 4-fold, respectively) and above 8 dyne/cm 2 expression was suppressed below that of untreated endothelial cells. In contrast, ICAM-1 expression and NFκB nuclear translocation increased with shear stress up to a maximum at 9 dyne/cm 2 . Monocyte recruitment was most efficient in regions where E-selectin and VCAM-1 expression was greatest.Conclusions-We found that the endothelium can sense a change in shear stress on the order of 0.25 dyne/cm 2 over a length of ~10 cells, regulating the level of protein transcription, cellular adhesion molecule expression, and leukocyte recruitment during inflammation.