Endothelial calcium signaling in rabbit arteries and its local alterations in early-stage atherosclerosis

This study is to examine whether endothelial calcium signaling is different between atherosclerosis-prone thoracic aortas (TA) and atherosclerosis-resistant carotid arteries (CA) in normal rabbits and how it changes in early-stage atherosclerosis. Local endothelial calcium signaling was examined in arterial segments obtained from rabbits fed with normal or high-cholesterol diet for 1-4 weeks. Contrasting to normal CA, normal TA showed lower endothelial calcium signaling with more concentrated NF-kappaB in the endothelial nuclei. In the same hypercholesterolemic animal, fatty streak formation was much more prominent in TA than in CA. TA endothelial calcium signaling became augmented in the second week of hypercholesterolemia, being most pronounced in smooth regions adjacent to miniature fatty streaks. It was sporadically elevated even in regions away from any detectable TA fatty streak. When the entire TA was covered with fatty streaks in the fourth week of hypercholesteremia, endothelial calcium signaling returned to the original level. In comparison, CA endothelial calcium signaling was reduced around scattered fatty streaks. Reduced calcium signaling happened where CA fatty streaks were 150 microm long (covering 15-30 cells); and it extended to areas adjacent to larger fatty streaks. Moreover, NF-kappaB remained in the cytosol of endothelial cells covering CA fatty streaks. Our results indicate that inter-vascular differences in endothelial calcium signaling may provide partial explanation in their differential susceptibility in atherosclerosis.