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By using specific anti-ACAT-1 antibodies in immunodepletion studies, we previously found that ACAT-1, a 50-kDa protein, plays a major catalytic role in the adult human liver, adrenal glands, macrophages, and kidneys but not in the intestine. Acyl-coenzyme A:cholesterol acyltransferase (ACAT) activity in the intestine may be largely derived from a different ACAT protein. To test this hypothesis, we produced specific polyclonal anti-ACAT-2 antibodies that quantitatively immunodepleted human ACAT-2, a 46-kDa protein expressed in Chinese hamster ovary cells. In hepatocyte-like HepG2 cells, ACAT-1 comprises 85-90% of the total ACAT activity, with the remainder attributed to ACAT-2. In adult intestines, most of the ACAT activity can be immunodepleted by anti-ACAT-2. ACAT-1 and ACAT-2 do not form heterooligomeric complexes. In differentiating intestinal enterocyte-like Caco-2 cells, ACAT-2 protein content increases by 5-10-fold in 6 days, whereas ACAT-1 protein content remains relatively constant. In the small intestine, ACAT-2 is concentrated at the apices of the villi, whereas ACAT-1 is uniformly distributed along the villus-crypt axis. In the human liver, ACAT-1 is present in both fetal and adult hepatocytes. In contrast, ACAT-2 is evident in fetal but not adult hepatocytes. Our results collectively suggest that in humans, ACAT-2 performs significant catalytic roles in the fetal liver and in intestinal enterocytes. Acyl-coenzyme A:cholesterol acyltransferase (ACAT) 1 is an integral membrane protein located in the endoplasmic reticulum. It catalyzes the formation of cholesteryl esters from long

Polyunsaturated fatty acids (PUFAs) such as docosahexaenoic and eicosapentaenoic acids (DHA, EPA) exert ischemic anti-arrhythmic effects. However, their mechanism of action remains unknown. The present study was designed to investigate their potential effect on the regulation of the late sodium current as the basis for their ischemic anti-arrhythmic activity. Human isoforms of wild-type SCN5A and DeltaKPQ-mutated cardiac sodium channels were stably transfected in HEK 293 cells and, the resulting currents were recorded using the patch clamp technique in whole cell configuration. In addition to their effect to inhibit peak I(Na), acute application of DHA and EPA blocked veratridine-induced late sodium current (late I(Na-Verat)) in a concentration--dependent manner with IC(50) values of 2.1 +/- 0.5 microM and 5.2 +/- 0.8 microM,for DHA and EPA, respectively. Channels availability was reduced, resulting in a significant leftward shift of the steadystate inactivation curve by -10.0 +/- 2.1 mV and -8.5 +/- 0.2 mV for DHA and EPA, respectively. Similar inhibitory effects of DHA and EPA were also observed on late I(Na-KPQ). In addition to their role as blocking agents of peak I(Na), DHA and EPA reduced human late I(Na). These results could explain the antiarrhythmic properties of DHA and EPA during ischemia or following ischemia-reperfusion.

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A series of 3-substituted (aryloxy)silane derivatives of benzylamine (4, 4', or 4") was synthesized and evaluated for hypocholesterolemic activity. Most of the new silane derivatives were identified as potent inhibitors of pig liver squalene epoxidase with IC50 values in the submicromolar range. In vitro inhibition of cholesterol biosynthesis in Hep-G2 cells was observed with a very good potency for the ene-yne derivatives 4a, 4i, 4n, 4q, and 4u as well as for the yne-yne compound 4". In vivo, 4i, 4u, 4', and 4" were found to decrease cholesterol biosynthesis in rats upon oral administration with ED50 values in the range of 2-7 mg/kg. Therefore, these new (aryloxy)methylsilane derivatives of benzylamine represent a new class of potent squalene epoxidase inhibitors with promising hypocholesterolemic properties.