👤 Daniel S Donovan

We report the discovery of a chemical series that enhances ApoE secretion from human astrocytes through mechanisms independent of LXR agonism. Target deconvolution of hits from a phenotypic screen in astrocytoma cells employed chemoproteomics, photoaffinity probes, in vitro KINOMEscan analysis, and targeted siRNA knockdown experiments. Photoaffinity labeling coupled with quantitative chemical proteomics identified aryl hydrocarbon receptor (AhR), a transcription factor not previously associated with ApoE secretion, as the primary target. A diverse panel of AhR agonists and antagonists together with genetic knockdown confirmed that ApoE secretion increases when AhR activity is reduced. Using a luciferase reporter assay, we demonstrated that active series analogs exhibit AhR antagonism while inactive compounds do not. Since deletion of AhR has severe peripheral effects, chronic inhibition of AhR is not an attractive therapeutic approach for Alzheimer's disease; nevertheless, these results position AhR as a modulator of ApoE secretion and a biological pathway worth exploring. Show less

Cholesteryl ester transfer protein (CETP) mediates the transfer of HDL cholesteryl esters for triglyceride (TG) in VLDL/LDL. CETP inhibition, with anacetrapib, increases HDL-cholesterol, reduces LDL-cholesterol, and lowers TG levels. This study describes the mechanisms responsible for TG lowering by examining the kinetics of VLDL-TG, apoC-II, apoC-III, and apoE. Mildly hypercholesterolemic subjects were randomized to either placebo (N = 10) or atorvastatin 20 mg/qd (N = 29) for 4 weeks (period 1) followed by 8 weeks of anacetrapib, 100 mg/qd (period 2). Following each period, subjects underwent stable isotope metabolic studies to determine the fractional catabolic rates (FCRs) and production rates (PRs) of VLDL-TG and plasma apoC-II, apoC-III, and apoE. Anacetrapib reduced the VLDL-TG pool on a statin background due to an increased VLDL-TG FCR (29%; Show less

Congenital malformations of the heart and circulatory system are the most common type of human birth defect. Recent studies have implicated the Notch signaling pathway in human cardiac development by demonstrating abnormalities of the JAG1 gene as the basis for Alagille syndrome and some cases of isolated tetralogy of Fallot or pulmonic stenosis. How the Notch pathway acts in cardiac development remains unknown, but the Hey family of basic helix-loop-helix (bHLH) transcription factors are candidates for mediating Notch signaling in the developing cardiovascular system. Here, we use gene targeting to determine the developmental functions of mouse Hey2, a Hey family member that is expressed during the embryonic development of the heart, arteries, and other organs. Homozygotes for the Hey2 mutant allele display a spectrum of cardiac malformations including ventricular septal defects, tetralogy of Fallot, and tricuspid atresia, defects that resemble those associated with mutations of human JAG1. These results establish Hey2 as an important regulator of cardiac morphogenesis and suggest a role for Hey2 in mediating or modulating Notch signaling in the developing heart. Show less