Deficiency in inducible nitric oxide synthase results in reduced atherosclerosis in apolipoprotein E-deficient mice

Inducible NO synthase (iNOS) present in human atherosclerotic plaques could contribute to the inflammatory process of plaque development. The role of iNOS in atherosclerosis was tested directly by evaluating the development of lesions in atherosclerosis-susceptible apolipoprotein E (apoE)-/- mice that were also deficient in iNOS. ApoE-/- and iNOS-/- mice were cross-bred to produce apoE-/-/iNOS-/- mice and apoE-/-/iNOS+/+ controls. Males and females were placed on a high fat diet at the time of weaning, and atherosclerosis was evaluated at two time points by different methods. The deficiency in iNOS had no effect on plasma cholesterol, triglyceride, or nitrate levels. Morphometric measurement of lesion area in the aortic root at 16 wk showed a 30-50% reduction in apoE-/-/iNOS-/- mice compared with apoE-/-/iNOS+/+ mice. Although the size of the lesions in apoE-/-/iNOS-/- mice was reduced, the lesions maintained a ratio of fibrotic:foam cell-rich:necrotic areas that was similar to controls. Biochemical measurements of aortic cholesterol in additional groups of mice at 22 wk revealed significant 45-70% reductions in both male and female apoE-/-/iNOS-/- mice compared with control mice. The results indicate that iNOS contributes to the size of atherosclerotic lesions in apoE-deficient mice, perhaps through a direct effect at the site of the lesion.     

ApoE(-/-) mice develop atherosclerosis in the absence of complement component C5

Previous studies have suggested that the terminal complex of complement may contribute to the pathogenesis of atherosclerosis. C5b-9 complexes colocalize with the extracellular lipid in the aortic intima of hypercholesterolemic rabbits, and C6-deficient rabbits develop less atherosclerosis than controls. To test the role of complement in atherosclerosis in a different animal model, C5 deficient (C5def) mice were cross-bred with atherosclerosis susceptible apoE(-/-) mice, generating mice deficient in both apoE and C5 and control apoE(-/-) mice. Progeny were typed for C5 titer and serum cholesterol levels. Both male and female mice were fed a high fat diet from weaning until 22 weeks of age. At that time there were no significant differences in plasma cholesterol or triglycerides between apoE(-/-) control and apoE(-/-)/C5def groups. Morphometric analysis of the aortic root lesions gave mean (+/-SEM) lesion areas for male apoE(-/-) and apoE(-/-)/C5def mice of 468,176 +/- 21,982 and 375,182 +/- 53,089 microm(2), respectively (n = 10 each, P value = 0.123). In female apoE(-/-) mice (n = 5), the mean lesion area was 591,981 +/- 53,242 microm(2), compared to 618,578 +/- 83,457 microm(2) for female apoE(-/-)/C5def mice (n = 10) (P value = 0.835). Thus neither male nor female mice showed a significant change in lesion area when C5 was not present. In contrast to the case in the hypercholesterolemic rabbit, activation of the terminal complex of complement does not play a major role in the development of atherosclerosis in apoE(-/-) mice.     

31P nuclear magnetic resonance of metabolic changes associated with cyanide intoxication in the perfused rat liver.

Metabolic changes associated with cyanide intoxication were observed for the first time in perfused rat liver using ³¹P nuclear magnetic resonance (NMR) at 60.7 MHz. Well-oxygenated control livers showed strong ATP peaks and little discernable internal orthophosphate (Pi). Perfusion with 2 mM cyanide eliminated the observable ATP peaks and caused internal Pi to increase. Despite clear evidence for ATP hydrolysis, resonances from cytoplasmic ADP were conspicuously absent. Resumption of perfusion with cyanide-free buffer caused a dramatic return of the ATP peaks with a concomitant fall in internal Pi. These metabolic changes are consistent with reversible binding of cyanide to mitochondrial cytochromes and their observation by ³¹P NMR indicates the potential of this method for studying metabolism in whole, perfused rat liver under physiologic conditions.