No abstract

Endothelial sequestration of circulating monocytes is a key event in early atherosclerosis. Hemodynamics is proposed to regulate monocyte-endothelial cell interactions by direct cell activation and establishment of flow environments that are conducive or prohibitive to cell-cell interaction. We investigated fluid shear regulation of monocyte-endothelial cell adhesion in vitro using a disturbed laminar shear system that models in vivo hemodynamics characteristic of lesion-prone vascular regions. Human endothelial cell monolayers were flow conditioned for 6 h before evaluation of monocyte adhesion under static and dynamic flow conditions. Results revealed a distinctive clustered cell pattern of monocyte adhesion that strongly resembles in vivo leukocyte adhesion in early- and late-stage atherosclerosis. Clustered monocyte cell adhesion correlated with endothelial cells coexpressing intercellular adhesion molecule-1 (ICAM-1) and E-selectin as result of a flow-induced, selective upregulation of E-selectin expression in a subset of ICAM-1-expressing cells. Clustered monocyte cell adhesion assayed under static conditions exhibited a spatial variation in size and frequency of occurrence, which demonstrates differential regulation of endothelial cell adhesiveness by the local flow environment. Dynamic adhesion studies conducted with circulating monocytes resulted in clustered cell adhesion only within the disturbed flow region, where the monocyte rate of motion is sufficiently low for cell-cell interaction. These studies provide evidence and reveal mechanisms of local hemodynamic regulation of endothelial adhesiveness and endothelial monocyte interaction that lead to localized monocyte adhesion and potentially contribute to the focal origin of arterial diseases such as atherosclerosis.

A chemoenzymatic route for the production of an intermediate to a gamma secretase inhibitor is described. The route is robust and was run at multikilogram scale. The process employs both a transaminase catalyzed reductive amination of a substituted tetralone and an alcohol dehydrogenase catalyzed reduction of an α-ketoester to generate the two chiral centers in the molecule, with nearly perfect stereoselectivity. The process also features simple isolation schemes, including a direct drop isolation of the aminotetralin phosphate salt.

Biocatalytic reductive amination catalyzed by engineered imine reductase (RedAms) is a new and powerful tool for the synthesis of substituted chiral amines. Herein, we describe a streamlined synthesis of compound 3, a key intermediate to a CDK 2/4/6 inhibitor 1, relying on the enzymatic reductive amination of a hydroxyketone to introduce the chiral secondary amine with high diastereoselectivity. The improved synthesis of the hydroxyketone precursor by a titanium-catalyzed reductive cyclization and the process development for two SNAr reactions en route to 3 are also presented.

Adenosine triphosphate (ATP)-citrate iyase (ACL) is a homotetrameric liver enzyme which catalyzes the cytosolic formation of acetyl-CoA. This reaction provides the major source of acetyl-CoA for fatty acid and cholesterol biosynthesis. Inhibition of ACL offers a potentially unique way to control plasma cholesterol and triglyceride levels. In this study, we describe the activity of an active microbial metabolite derived from a soil fungus, Penicillium sp., SC2193. This culture produces a series of related anthrones and anthraquinones. We present evidence for one of these anthrones, 2-chloro-1,3,8-trihydroxy-6-methyl-9-anthrone, as a specific and competitive inhibitor of ACL against the substrate Mg citrate and mixed noncompetitive inhibition against two other required substrates for this enzyme, M g ATP and CoA. With an I C , , of 283 n M in the primary assay and, more specifically, a Ki of 4 0 0 n M against the substrate M g citrate, SC2193 represents the most potent competitive inhibitor of ACL yet described, and, as such, might prove very useful as a molecular tool for the discovery of selective, mechanistically novel hypolipidernic agents. 0 1995 Wiley-Liss, Inc.