Role of oxidative stress on pathogenesis of hypertensive cerebrovascular lesions.

The hypertensive rat brain exhibited softening, severe edema and intracerebral hemorrhage. The NO(2) (-) + NO(3) (-) (NOx) level in the hypertensive rat brain was higher than in the normotensive rat brain. Light microscopy demonstrated severe arterial and arteriolar lesions with fibrinoid deposits and medial lesion. After injecting hypertensive rats with nitroblue tetrazolium (NBT), formazan deposits, which are the reaction product of reduction of NBT by superoxide, were observed in the microvessels and nervous tissue around the microvessels of injured brain. Immunohistochemistry showed that copper zinc superoxide dismutase and manganese superoxide dismutase expression of the endothelial cells of hypertensive rats were also upregulated in comparison with normotensive rat endothelial cells. Inducible nitric oxide synthase and endothelial nitric oxide synthase expression in endothelial cells of normotensive rats were strongly positive, whereas the expression in hypertensive rat endothelial cells was weaker. Nitrotyrosine, a biomarker of peroxynitrite, which is a powerful oxidant formed by the reaction of nitric oxide (NO) with superoxide, was found in the microvessels, injured arteries and arterioles and infarcted brain tissue. Deposition of a major aldehydic product of lipid peroxidation, that is, 4-hydroxy-2-nonenal (4-HNE) was found in microvessels, perivascular tissue, and edematous and infarcted brain. Hypertensive cerebrovascular disease is the result of hypertension-induced oxidative stress.