Hyperlipidemia induced by a cholesterol-rich diet leads to enhanced peroxynitrite formation in rat hearts

Objective: We investigated the influence of experimental hyperlipidemia on the formation of cardiac NO, superoxide, and peroxynitrite (ONOO-) in rat hearts. Methods: Wistar rats were fed 2% cholesterol-enriched diet or normal diet for 8 weeks. Separate groups of normal and hyperlipidemic rats were injected twice intraperitoneally with 2X20 mumol/kg FeTPPS (5,10,15,20-tetrakis-[4-sulfonatophenyl] -porphyrinato-iron [111]), a ONOO- decomposition catalyst, 24 h and I h before isolation of the hearts. Results: A cholesterol diet significantly decreased myocardial NO content, however, myocardial Ca2+-dependent and Ca2+-independent NO synthase activity and NO synthase protein level did not change. Myocardial superoxide formation and xanthine oxidase activity were significantly increased; however, cardiac superoxide dismutase activity did not change in the cholesterol-fed group. Dityrosine in the perfusate, a marker of cardiac ONOO- formation, and plasma nitrotyrosine, a marker for systemic ONOO- formation, were both elevated in hyperlipidemic rats. In cholesterol-fed rats, left ventricular end-diastolic pressure (LVEDP) was significantly elevated as compared to controls. Administration of FeTPPS normalized LVEDP in the cholesterol-fed group. Conclusion: We conclude that cholesterol-enriched diet-induced hyperlipidemia leads to an increase in cardiac ONOO- formation and a decrease in the bioavailability of NO which contributes to the deterioration of cardiac performance and may lead to further cardiac pathologies. (C) 2003 European Society of Cardiology. Published by Elsevier Science B.V. All rights reserved.