Background
The aim of our study was to explore the effect of high-cholesterol diet and preconditioning on cardiac gene expression patterns in mouse hearts, focusing on genes involved in nitric oxide (NO) and free radical signaling and the mevalonate pathway.
Material and Method
Mice were fed 2% high-cholesterol or normal diet for 8 weeks. Hearts isolated from both groups were subjected to either a preconditioning (PC) protocol (3 cycles of 5 min ischemia and 5 min aerobic perfusion) or a time-matched non-preconditioning protocol followed by 30 min global test ischemia and 2 hour reperfusion.
Results
PC altered gene expression only in the mice subjected to a normal diet, as shown in neuronal nitric oxide synthase (nNOS), endothelial nitric oxide synthase (eNOS) and the superoxide-producing enzymes xanthine oxidase (XO) and nicotinamide adenine dinucleotide phosphate (NADPH) oxidases 1 and 4. The rate-limiting enzyme of the mevalonate pathway, 3-Hydroxy-3-methylglutaryl-coenzyme A (HMG-CoA) reductase showed differential expression in the myocardium in response to I/R and PC in mice on normal diet but not in cholesterol-fed animals.
Conclusions
We conclude that cholesterol-enriched diet leads to alterations in preconditioning-induced gene expression in the mouse heart, which might lead to marked changes of oxidative/nitrosative stress signaling and to the attenuation of the cardioprotective effect of preconditioning.

Keywords: Oxidative Stress - physiology, Nitric Oxide Synthase - metabolism, NADPH Oxidase - metabolism, NADH, NADPH Oxidoreductases - metabolism, Myocardium - metabolism, Mevalonic Acid - metabolism, Ischemic Preconditioning, Myocardial, Hypercholesterolemia - metabolism, Heart - physiology, Gene Expression Regulation - physiology, DNA Primers - genetics, Cholesterol, Dietary - toxicity, Analysis of Variance, Reverse Transcriptase Polymerase Chain Reaction, Xanthine Oxidase - metabolism