Objective-Vascular endothelial cells (ECs) are subjected to shear stress and cytokine stimulation. We studied the interplay between shear stress and cytokine in modulating the expression of adhesion molecule genes in ECs. Methods and Results-Shear stress (20 dynes/cm2 ) was applied to ECs prior to and/or following the addition of tumor necrosis factor (TNF)-␣. Shear stress increased the TNF-␣-induced expression of intercellular adhesion molecule-1 (ICAM-1) at both mRNA and surface protein levels, but decreased the TNF-␣-induced expression of vascular adhesion molecule-1 (VCAM-1) and E-selectin. Transfection studies using promoter reporter gene constructs of ICAM-1, VCAM-1, and E-selectin demonstrated that these shear stress modulations of gene expression occur at the transcriptional levels. After 24-hour preshearing followed by 1 hour of static incubation, the effect of preshearing on TNF-␣-induced ICAM-1 mRNA expression vanished. The recovery of the TNF-␣-induced VCAM-1 and E-selectin mRNA expressions following preshearing, however, required a static incubation time of Ͼ6 hours (complete recovery at 24 hours). Pre-and postshearing caused a reduction in the nuclear factor-B-DNA binding activity induced by TNF-␣ in the EC nucleus. V ascular endothelial cells (ECs) are constantly exposed to fluid shear stress, a tangential force generated by the velocity gradient in viscous fluid flow. The nature and magnitude of shear stress play a significant role in the homeostasis of the structure and function of the blood vessel. Recent evidence suggests that physiological levels of laminar shear stress modulate cellular signaling and EC function and are protective against atherogenesis. 1 In human carotid and coronary arteries, atherosclerotic plaques are found in the vicinity of arterial bifurcations and bends, where the local flow is disturbed. 2 In contrast, regions of artery that experience laminar non-oscillatory shear stress were protected from atherosclerosis. The cytokine tumor necrosis factor-␣ (TNF-␣) is an important mediator of the inflammatory processes that occur during the progression of atherosclerosis. 3 Produced by macrophages that infiltrate the lesion, cytokines such as TNF-␣ are known to induce the expression of many endothelial genes that contribute to the complex processes involved in atherogenesis. 3 Well know examples include the transcriptional regulation of various adhesion molecules, such as intercellular adhesion molecule-1 (ICAM-1), vascular cell adhesion molecule-1 (VCAM-1), and E-selectin. 3 In contrast to laminar shear stress, cytokines are generally considered to be proatherogenic factors. Conclusions-OurDespite the intensive studies on the effects of fluid shear stress on ECs, the interplay of shear stress and cytokines in modulating EC gene expression and function has not fully been clarified. It has been shown that physiological levels of laminar shear stress inhibit the apoptosis of ECs induced by TNF-␣ and H 2 O 2 . 4,5 This inhibitory effect of shear stress is mediated by signalin...

CD200 is a highly glycosylated cell surface protein containing two immunoglobulin superfamily domains in the extracellular region and performs immunosuppressive activities. It is widely distributed in various tissues including the vascular endothelium. We report here the distribution of CD200 in rat endothelia from different vascular beds. Endothelial CD200 immunoreactivity was weakly expressed in most arteries but was intensely expressed in the arterioles, most veins and venules, as well as continuous and fenestrated capillaries. The distribution of CD200 in the sinusoidal and lymphatic endothelia was variable. Immunoelectron microscopic studies revealed that endothelial CD200 varied considerably not only in different microvasculatures but also in the membrane domains at the subcellular level. Endothelial CD200 expression was differentially regulated by lipopolysaccharide in cell types both in vivo and in vitro . Functional assessments of endothelial CD200 suggested that the physical binding between CD200 and CD200 receptor (CD200R) was involved in T-cell adhesion to the endothelium but not in macrophageendothelium interaction. In the latter, however, CD200 agonist, a synthetic peptide from complementaritydetermining region 3 of mouse CD200, may trigger CD200R signaling in macrophages to suppress their adhesion to the endothelium. Our findings demonstrate that the distribution, subcellular localization, and lipopolysaccharideregulation of endothelial CD200 are heterogeneous, and provide evidence elucidating the functional roles of endothelial CD200 during tissue inflammation.

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Internal tandem duplication of FLT3 juxtamembrane domain (FLT3-ITD)-positive acute myeloid leukemia (AML) leads to poor clinical outcomes after chemotherapy. We aimed to establish a cytarabine-resistant line from FLT3-ITD-positive MV4-11 (MV4-11-P) cells and examine the development of resistance. The FLT3-ITD mutation was retained in MV4-11-R; however, the protein was underglycosylated and less phosphorylated in these cells. Moreover, the phosphorylation of ERK1/2, Akt, MEK1/2 and p53 increased in MV4-11-R. The levels of Mcl-1 and p53 proteins were also elevated in MV4-11-R. A p53 D281G mutant emerged in MV4-11-R, in addition to the pre-existing R248W mutation. MV4-11-P and MV4-11-R showed similar sensitivity to cabozantinib, sorafenib, and MK2206, whereas MV4-11-R showed resistance to CI-1040 and idarubicin. MV4-11-R resistance may be associated with inhibition of Akt phosphorylation, but not ERK phosphorylation, after exposure to these drugs. The multi-kinase inhibitor cabozantinib inhibited FLT3-ITD signaling in MV4-11-R cells and MV4-11-R-derived tumors in mice. Cabozantinib effectively inhibited tumor growth and prolonged survival time in mice bearing MV4-11-R-derived tumors. Together, our findings suggest that Mcl-1 and Akt phosphorylation are potential therapeutic targets for p53 mutants and that cabozantinib is an effective treatment in cytarabine-resistant FLT3-ITD-positive AML.