J-104,871, a novel farnesyltransferase inhibitor, blocks Ras farnesylation in vivo in a farnesyl pyrophosphate-competitive manner.

Farnesylation of the activated ras oncogene product by protein farnesyltransferase (FTase) is a critical step for its oncogenic function. Because squalene synthase and FTase recruit farnesyl pyrophosphate as a common substrate, we modified squalene synthase (SS) inhibitors to develop FTase inhibitors. Among the compounds tested, a novel FTase inhibitor termed J-104,871 inhibited rat brain FTase with an IC50 of 3.9 nM in the presence of 0.6 microM farnesyl pyrophosphate (FPP), whereas it scarcely inhibited rat brain protein geranylgeranyltransferase-I or SS. The in vitro inhibition of rat brain FTase by J-104,871 depends on the FPP concentration but not on the concentration of Ras peptide. Thus, in vitro studies strongly suggest that J-series compounds have an FPP-competitive nature. J-104,871 also inhibited Ras processing in activated H-ras-transformed NIH3T3 cells with an IC50 value of 3.1 microM. We tested the effects of lovastatin and zaragozic acid A, which modify cellular FPP levels, on Ras processing of J-104,871. Lovastatin, a hepatic hydroxymenthyl coenzyme A reductase inhibitor that reduced the cellular FPP pool, increased the activity of J-104,871, whereas 3 microM zaragozic acid A, an SS inhibitor that raised the FPP level, completely abrogated the activity of J-104,871 even at 100 microM. These results suggest that J-104,871 inhibits FTase in an FPP-competitive manner in whole cells as well as in the in vitro system. Furthermore, J-104,871 suppressed tumor growth in nude mice transplanted with activated H-ras-transformed NIH3T3 cells.

Cholesterol lowering in low density lipoprotein receptor knockout mice overexpressing apolipoprotein E.

Apo E is a key molecule in the lipoprotein metabolism; thus, genetic manipulation of apo E may prove useful in the treatment of hypercholesterolemia. To test the feasibility of this idea, we have generated low density lipoprotein receptor (LDLR) knockout mice that overexpress the rat apo E transgene (ETg+/+:LDLRKO), and compared their plasma lipoprotein profiles with those of nonexpressing LDLR knockout mice (ETg-/-:LDLRKO). On a normal chow diet, the mean plasma cholesterol level of ETg+/+:LDLRKO mice was significantly lower than that of ETg-/-:LDLRKO mice (189 versus 240 mg/dl, P < 0. 01). The LDL fraction was selectively reduced in the ETg+/+:LDLRKO mice. Despite the challenge with an atherogenic diet, cholesterol lowering was persistently observed and fatty streak lesions in the aortic sinus were significantly suppressed in the mice overexpressing apo E. These results imply that stimulation of hepatic production of apo E may be used as a promising adjunctive therapy for homozygous familial hypercholesterolemia.

N-[2-[N'-pentyl-(6,6-dimethyl-2,4-heptadiynyl)amino]ethyl]- (2-methyl-1-naphthylthio)acetamide (FY-087). A new acyl coenzyme a:cholesterol acyltransferase (ACAT) inhibitor of diet-induced atherosclerosis formation in mice.

FY-087 (N-[2-[N'-pentyl-(6,6-dimethyl-2,4-heptadiynyl)amino]ethyl]- (2-methyl-1-naphthylthio)acetamide) was found to be a competitive inhibitor of human microsomal acyl coenzyme A:cholesterol acyltransferase (ACAT) with an IC50 value of 0.11 microM. Under our assay conditions, other ACAT inhibitors tested, specifically YM-750, E-5324, and melinamide, all of which are now in phase I clinical trials or in clinical use in Japan, inhibited this enzyme with IC50 values of 0.18, 0.14, and 3.2 microM, respectively. FY-087 also inhibited ACAT in acetyl-low density lipoprotein loaded human macrophages (THP-1 cells) with an IC50 of 0.17 microM. Following the oral administration of FY-087 (30 mg/kg) to rats, the plasma concentration of FY-087 reached 0.42 microgram/mL after 2 hr. This concentration of FY-087 was enough to inhibit blood vessel ACAT activity. Cholesterol-lowering and anti-atherogenic effects of FY-087 were examined using C57BL/6J mice fed an atherogenic diet. In this mouse model, treatment with FY-087 (28 mg/kg) inhibited the increase in plasma cholesterol levels by about 20% and decreased the hepatic accumulation of free and esterified cholesterol by 61 and 67%, respectively. FY-087 also significantly inhibited the atherogenic diet-induced increase in the fatty-streak lesion area of the proximal aorta by 57% in C57BL/6J mice. These results indicate that FY-087 is not only a therapeutically bioavailable ACAT inhibitor that lowers plasma cholesterol levels, but also an effective anti-atherogenic agent in mice fed an atherogenic diet.

Inhibition of cultured vascular smooth muscle cell migration by simvastatin (MK-733).

The effect of simvastatin (MK-733), a potent 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase inhibitor, on the migration of cultured porcine smooth muscle cells (SMCs) was investigated in modified Boyden chambers. Platelet-derived growth factor (PDGF) stimulated the SMC migration dose dependently. MK-733 inhibited the migration response induced by PDGF with an IC50 value of 2 microM. Supplementation with mevalonate restored the migration response inhibited by MK-733 but the addition of low-density-lipoprotein (LDL) did not change the response. Another HMG-CoA reductase inhibitor, pravastatin (CS-514), also reduced the migration response. However its potency was far less than that of MK-733. MK-733 also inhibited the SMC migration stimulated by fibrinogen. These results suggest that non-sterol metabolite(s) of mevalonate, possibly prenylated proteins, are involved in a migration signaling pathway and that HMG-CoA reductase inhibitors are effective in the prevention of the formation of intimal hyperplasia in atherosclerosis.

Effect of an inhibitor of squalene epoxidase, NB-598, on lipid metabolism in Hep G2 cells.

NB-598, a potent inhibitor of squalene epoxidase, inhibited cholesterol synthesis from [14C]acetate and induced intracellular squalene accumulation in Hep G2 cells. NB-598 inhibited cholesterol synthesis from [14C]acetate, [3H]mevalonate, and [3H]squalene, but not from [3H]2,3-oxidosqualene in Hep G2 cells. It reduced cholesterol ester synthesis remarkably in the absence of exogenous cholesterol. This compound did not have any effect on the synthesis of ubiquinone and dolichol. When Hep G2 cells were prelabeled with micellar [3H]cholesterol, NB-598 did not affect the excretion of bile acid incorporated from [3H]cholesterol. However, NB-598 decreased the secretion of free and esterified cholesterol, triacylglycerol, and phospholipids, and increased the secretion of squalene. NB-598 is thought not only to inhibit cholesterol synthesis, but also to inhibit the secretion of lipids.