Abstract 2326: Severe Dyslipidemia and Lipid-Rich Atherosclerotic Lesion Formation in Mice Lacking All Nitric Oxide Synthases Fed a High-Cholesterol Diet
Background: We have recently developed mice lacking all 3 nitric oxide synthases (nNOS, iNOS, and eNOS) (PNAS 2005). In this study, we examined the effects of a high-cholesterol diet on lipid metabolism and vascular lesion formation in those mice.
Methods and Results: Experiments were performed in 4-month-old male wild-type (WT), singly nNOS−/−, iNOS−/−, eNOS−/−, and triply n/i/eNOS−/− mice maintained on either a regular diet or a high-cholesterol diet for 3 months. The high-cholesterol feeding significantly increased plasma levels of total cholesterol (TC) and low-density lipoprotein cholesterol (LDL) in all the genotypes as compared on the regular diet (all P<0.05, n=6–8). The plasma levels of TC and LDL on the high-cholesterol diet (mg/dl) were significantly higher in the singly nNOS−/− (473±124 and 312±141), iNOS−/− (549±152 and 341±151), eNOS−/− (618±63 and 395±70), and the triply n/i/eNOS−/− mice(2316±1991 and 1326±43) than in the WT mice (326±43 and 244±54) (all P<0.05, n=6–8). Notably, the extents of the dyslipidemia were markedly accelerated in the triply NOS−/− mice when compared with the 3 singly NOS−/− genotypes (all P<0.05, n=6–8). Furthermore, lipid accumulation in the aorta by the high-cholesterol diet (lipid area, %, Oil red O staining) were also significantly accelerated in the singly nNOS−/− (7.1±4.0), iNOS−/−(6.6±5.0), eNOS−/− (5.5±5.1), and the triply n/i/eNOS−/− mice (20.6±1.0) than in the WT mice (3.6±1.2), while the extent of the aortic atherosclerosis was again markedly greater in the triply NOS−/− mice compared with the 3 singly NOS−/− genotypes (all P<0.05, n=7–9). Importantly, in the aorta of the 3 singly NOS−/− genotypes, other NOSs that had not been disrupted were expressed (n=6–7). In singly eNOS−/− mice, nNOS expression in the aorta was significantly up-regulated compared with WT mice (2.1 folds), whereas in the triply n/i/eNOS−/−mice, such NOS expression was totally absent (Western blotting) (n=6–7), suggesting the compensation among NOSs in the singly NOS−/− mice.
Conclusions: These results indicate that a high-cholesterol diet causes severe dyslipidemia and lipid-rich atherosclerotic aortic lesion under genetic disruption of all NOSs, suggesting a critical role of whole NOSs system in preventing those disorders.