EXPRESSION OF INDUCIBLE NITRIC-OXIDE SYNTHASE IN T-LYMPHOCYTES AND MACROPHAGES IN VESSELS WITH ADVANCED ATHEROSCLEROSIS

While endothelial nitric oxide synthase is expressed in the endothelia l cells of normal and atherosclerotic vessels, there are few reports a bout inducible nitric oxide synthase (iNOS) in atheroma. We investigat ed the expression of iNOS and its relation to inflammatory cells in at heroma. New Zealand White rabbits received a 1% cholesterol diet for 9 weeks (atherogenic diet) or a 1% cholesterol diet for 9 weeks then a normal diet for 36 weeks (reversible diet). The aortas were examined b y immunohistochemical staining for anti-iNOS antibody, as well as anti bodies for macrophages, T lymphocytes, and muscle actin. No iNOS was d etected in normal aortas, intimal thickening, or fatty streaks. althou gh iNOS was detected in advanced plaques, it was not seen in smooth mu scle-derived cells or endothelial cells, but was found in some macroph age-derived cells and in T lymphocytes. In regressive atherosclerotic aortas, iNOS was detected only in advanced plaques and net in macropha ge-derived cells, but in T lymphocytes. These findings suggest that T lymphocytes and some macrophages induce iNOS through cytokine producti on in atheroma.