A selective ACAT-1 inhibitor, K-604, suppresses fatty streak lesions in fat-fed hamsters without affecting plasma cholesterol levels.

BACKGROUND: Acyl-coenzyme A:cholesterol O-acyltransferase-1 (ACAT-1), a major ACAT isozyme in macrophages, plays an essential role in foam cell formation in atherosclerotic lesions. However, whether pharmacological inhibition of macrophage ACAT-1 causes exacerbation or suppression of atherosclerosis is controversial. METHODS AND RESULTS: We developed and characterized a novel ACAT inhibitor, K-604. The IC(50) values of K-604 for human ACAT-1 and ACAT-2 were 0.45 and 102.85 micromol/L, respectively, indicating that K-604 is 229-fold more selective for ACAT-1. Kinetic analysis indicated that the inhibition was competitive with respect to oleoyl-coenzyme A with a K(i) value of 0.378 micromol/L. Exposure of human monocyte-derived macrophages to K-604 inhibited cholesterol esterification with IC(50) of 68.0 nmol/L. Furthermore, cholesterol efflux from THP-1 macrophages to HDL(3) or apolipoprotein A-I was enhanced by K-604. Interestingly, administration of K-604 to F1B hamsters on a high-fat diet at a dose of >or=1mg/kg suppressed fatty streak lesions without affecting plasma cholesterol levels. CONCLUSIONS: K-604, a potent and selective inhibitor of ACAT-1, suppressed the development of atherosclerosis in an animal model without affecting plasma cholesterol levels, providing direct evidence that pharmacological inhibition of ACAT-1 in the arterial walls leads to suppression of atherosclerosis.

Influence of 3-hydroxy-3-methylglutaryl coenzyme A reductase inhibitors on ubiquinone levels in rat skeletal muscle and heart: relationship to cytotoxicity and inhibitory activity for cholesterol synthesis in human skeletal muscle cells.

Although statins are prescribed as relatively safe and effective drugs for hypercholesterolemic patients, it has been reported that a significant side effect, myopathy, occurs infrequently during medication. Moreover, because statins decrease cardiac ubiquinone levels, the risk of cardiac dysfunction has been suggested. This study sought to evaluate and compare the cytotoxicity of statins (cerivastatin, pitavastatin, fluvastatin, simvastatin, atorvastatin and pravastatin) in cultured human skeletal muscle cells (HSkMCs) and the effects on ubiquinone levels in statin-treated rat skeletal muscle and heart. Cerivastatin, the most potent inhibitor of HMG-CoA reductase, showed the strongest cytotoxicity (over 10-fold) among the statins examined, while the effects of the others were in a similar range. In rat experiments, neither pitavastatin nor cerivastatin decreased ubiquinone levels in skeletal muscle, but both dose-dependently lowered ubiquinone levels in the heart. As the rates of reduction by pitavastatin (9.6% at 30 mg/kg) and cerivastatin (9.7% at 0.3 mg/kg) were almost equal, it was estimated that cerivastatin reduced ubiquinone levels in the rat heart approximately 100-fold more strongly than pitavastatin, based on the effective doses. We found that cerivastatin showed the most potent cytotoxicity in HSkMCs and strongly lowered ubiquinone levels in the rat heart.

Augmented reduction of islet ß-cell mass in Goto-Kakizaki rats fed high-fat diet and its suppression by pitavastatin treatment.

UNLABELLED: Aims/Introduction: High fat diet (HFD) is known to be a risk for development of type 2 diabetes. It is unclear, however, how it affects the glucose tolerance or the islet structure in type 2 diabetes. The aim of this study is: (i) to examine the effects of HFD on the islet in GK rats, non-obese type 2 diabetic model; and (ii) to explore if pitavastatin treatment influences the change. MATERIALS AND METHODS: To see the effects of HFD on islet changes in type 2 diabetes, 4-week old male GK and Wistar rats were fed HFD for 16 weeks and subjected to glucose tolerance tests and pathological studies of the islet. The effects of pitavastatin (3 mg/kg/day for 16 weeks, oral), one of the lipophilc statins, were also examined in both GK and Wistrar rats fed with or without HFD. RESULTS: The HFD induced hyperlipidemia and aggravated glucose intolerance in both GK and Wistar rats. Pitavastatin treatment did not influence the glucose tolerance in HFD-fed animals. HFD caused an increase in hepatic lipid contents in all the animals, which was partially suppressed by pitavastatin treatment. GK rats showed reduced ß-cell mass, and fibrosis and macrophage migration in the islets. HFD feeding in GK rats augmented these changes which were associated with enhanced expression of 8-hydroxydeoxyguanosine and an increase in apoptotic cells. Pitavastatin treatment improved the HFD-induced islet pathology, and pancreatic insulin contents paralleled the structural changes. CONCLUSIONS: HFD feeding worsened the islet pathology in GK rats which was suppressed by pitavastatin treatment. (J Diabetes Invest, doi: 10.1111/j.2040-1124.2011.00173.x, 2011).

Route of penetration of topically instilled nipradilol into the ipsilateral posterior retina.

PURPOSE: To investigate how topically instilled nipradilol penetrates the ipsilateral posterior retina-choroid in normal rabbit eyes. METHODS: Albino rabbits were used. Topical instillation (1%, 100 microL) or intracameral (0.1%, 100 microL) or sub-Tenon injection (0.1%, 10 microL) of [(14)C]nipradilol was performed in one eye. Ocular and periocular distribution and the concentrations of [(14)C]nipradilol were determined by whole-head autoradiography, the results of which were validated by measurements in isolated tissues. In addition, the unchanged form of nonradiolabeled nipradilol in the posterior retina after topical instillation (1%, 100 microL) was quantified by liquid chromatography-tandem mass spectrometry (LC/MS/MS). RESULTS: Autoradiography revealed that the nipradilol concentration after topical instillation was higher in the ipsilateral posterior retina-choroid than on the contralateral side (142.9 ng/g vs. 108.3 ng/g, P = 0.026), and in the periocular tissue around the optic nerve insertion on the ipsilateral side than on the contralateral side (207.1 ng/g vs. 141.1 ng/g, P < 0.001). After intracameral injection, radioactivity was observed only in anterior, but not posterior parts of the eye. Radioactivity was observed only in the ipsilateral posterior retina-choroid and periocular tissues around the optic nerve insertion after sub-Tenon injection. The results in the isolated tissues validated autoradiographic evaluations. CONCLUSIONS: These results suggest that diffusion from posterior periocular tissues across the posterior sclera may be the main route for local penetration of the instilled drug to reach the posterior retina-choroid in albino rabbits.

Investigation of binding proteins for anti-platelet agent K-134 by Drug-Western method.

K-134 ((-)-6-[3-[3-cyclopropyl-3-[(1R, 2R)-2-hydroxycyclohexyl]ureido]-propoxy]-2(1H)-quinolinone) is a novel anti-platelet agent with anti-hyperplastic activities. We found previously that K-134 is a potent phosphodiesterase-3 (PDE3) inhibitor. In the present study, we found other K-134-binding proteins by Drug-Western method. We isolated two clones that can bind directly to K-134, cofilin-2, and CD36 in vitro. Comparison of their amino acid sequences showed similarity over a short stretch [KxxxxVxIxWxxE] in part in the collagen-binding region of CD36. K-134 inhibited binding between CD36 and collagen type-I; however, other PDE3 inhibitors, cilostazol, amrinone, and an inactive derivative of K-134, 4S-OH-K-134, showed little or no effect on binding. It was strongly suggested that the direct binding between K-134 and CD36 is a characteristic effect of K-134, and the homologous stretch may be necessary for binding to K-134. These results also suggested that these interactions are involved in the mechanisms of the anti-platelet and anti-hyperplastic effects of K-134.