Alterations in membrane-bound and cytoplasmic K-ras protein levels in mouse lung induced by treatment with lovastatin,cholestyramine, or niacin: effects are highly mouse strain dependent |
| |
Authors: | Calvert Richard J Ramakrishna Gayatri Tepper Shirley Diwan Bhalchandra A Anderson Lucy M Kritchevsky David |
| |
Institution: | Division of Research and Applied Technology, Office of Nutritional Products, Labeling and Dietary Supplements, Center for Food Safety and Applied Nutrition, U.S. Food and Drug Administration, Washington, DC, USA. calvert@mail.ncifcrf.gov |
| |
Abstract: | Agents that either increase (cholestyramine, CS) or decrease (lovastatin, Lov) de novo peripheral cholesterol synthesis may increase (CS) or decrease (Lov) ras protein membrane localization by altering protein prenylation, and potentially have pro- or anti-carcinogenic effects. Male A/J, Swiss, and C57/BL6 mice were treated with 2 or 4% CS, 1% dietary niacin, or 25mg/kg of Lov three times per week (Lov-3X) or five times per week (Lov-5X). After 3 weeks, serum cholesterol and triglycerides were determined enzymatically. Membrane and cytoplasmic K-ras proteins in lung were determined by immunoprecipitation followed by western blotting with a K-ras specific antibody. Results confirmed the hypothesis only in isolated instances. A/J mice had a significant 30% increase in cytoplasmic K-ras and a 40% decrease in membrane K-ras from Lov treatment, as predicted. C57/BL6 mice had a significant 77% increase in membrane K-ras, as expected from CS feeding. At variance with the hypothesis, Swiss mice had increased levels (3-28%) of membrane K-ras with all treatments (including Lov), and C57/BL6 mice treated with Lov had a 58-78% increase in cytoplasmic K-ras without any reduction in the levels of membrane K-ras. Niacin, predicted to have no effect on ras membrane localization, decreased cytoplasmic K-ras in A/J mice, increased both membrane and cytoplasmic K-ras in Swiss mice, and had no effect in C57/BL6 mice. Results may have differed from those predicted because of strain-dependent differences in response to the cholesterol-lowering agents. A difference in response among the mouse strains suggests that individual genetic differences may alter the effect of hypocholesterolemic agents on K-ras membrane localization, and potentially the risk of ras-dependent cancer. |
| |
Keywords: | CS cholestyramine DMBA 7 12-dimethylbenz[a]anthracene DTT DL-dithiothreitol" target="_blank">DL-dithiothreitol HMG-CoA reductase hydroxymethylglutaryl coenzyme A reductase Lov lovastatin Lov-3X lovastatin (25 mg/kg) three times per week Lov-5X lovastatin (25 mg/kg) five times per week PBS-T phosphate-buffered saline with 0 1% Tween 20 pH 7 5 PMSF phenylmethylsulfonyl fluoride |
本文献已被 ScienceDirect PubMed 等数据库收录! |
|