Abstract 5293: A New Animal Model of Hypercholesterolemia and Atherosclerosis: Mice Deficient in All Nitric Oxide Synthases

Abstract

We have recently developed mice lacking all three nitric oxide synthase (NOS) isoforms: nNOS, iNOS, and eNOS ( PNAS 2005). In this study, we examined the effects of a high-cholesterol (HC) diet on lipid metabolism and vascular lesion formation in those mice. Experiments were performed in 2-month-old male wild-type (WT) and singly, doubly, and triply NOS −/− mice (n=6–9). They were maintained on either a regular diet or a HC diet for 3 months. The HC feeding significantly increased plasma levels of total cholesterol (TC) and low-density lipoprotein cholesterol (LDL) in all the genotypes studied as compared on the regular diet (all P <0.05). These serum levels of TC and LDL on the HC diet (mg/dl) were both significantly higher in all the singly, doubly, and triply NOS −/− genotypes as compared with the WT genotype (singly nNOS −/− [371±61 and 205±65], iNOS −/− [559±62 and 350±62], eNOS −/− [619±22 and 395±25], doubly n/iNOS −/− [518±77 and 328±72], n/eNOS −/− [635±56 and 458.8±42], e/iNOS −/− [480±38 and 260±40], triply n/i/eNOS −/− [2316±704 and 1588±715], and WT [326±43 and 244±54]) (all P <0.05). Notably, the extent of the dyslipidemia was by far severest in the triply n/i/eNOS −/− genotype among the NOS −/− genotypes, and intriguingly, the serum levels of TC and LDL in the triply n/i/eNOS −/− genotype were equivalent to those in apolipoprotein E −/− mice that exhibit severe hypercholesterolemia. Lipid accumulation in the aorta on the HC diet (lipid area, %, oil red O staining) was also significantly more accelerated in all the NOS −/− genotypes than in the WT genotype (singly nNOS −/− [6.6±1.5], iNOS −/− [6.7±2.2], eNOS −/− [5.5±2.3], doubly n/iNOS −/− [4.7±1.7], n/eNOS −/− [6.4±1.4], i/eNOS −/− [6.8±1.3], triply n/i/eNOS −/− [20.6±1.0], and WT [3.6±1.2]), while the extent of the aortic atherosclerosis was again by far severest in the triply n/i/eNOS −/− genotype (all P <0.05). These results demonstrate that mice deficient in all NOSs manifest severe hypercholesterolemia and lipid-rich atherosclerotic lesion formation in response to a HC diet, indicating a pivotal role of the whole NOS system in preventing those disorders. Our triply NOS −/− mouse is a new experimental model of human hypercholesterolemia and atherosclerosis.