Proceedings of The Physiological Society

Physiology 2014 (London, UK) (2014) Proc Physiol Soc 31, C65

Oral Communications

Ca2+ signalling is differentially altered in endothelial cells from aortic arch and thoracic aorta in the Apolipoprotein E knockout mouse model of atherosclerosis

C. Prendergast1, J. Quayle1, T. Burdyga1, S. Wray1

1. Dept. Cellular & Molecular Physiology, University of Liverpool, Liverpool, United Kingdom.

ApoE-/- mice develop hypercholesterolemia and are a widely used model of atherosclerosis. Changes in Ca2+ are vital to the function of endothelial cells, but how atherosclerosis changes these signals is unclear. We examined the effect of hypercholesterolemia on Carbachol (CCh)-mediated Ca2+ signals in aortic endothelial cells from WT and ApoE-/- mice at 10 weeks (young), before plaques; 24 weeks, when plaques are established and 30 weeks, when plaques are extensive. Using confocal microscopy, we compared CCh (0.3-10μM) responses in thoracic aorta (TA) and the more plaque-prone aortic arch (AA). In addition, in older ApoE-/- mice, measurements were taken from endothelial cells immediately adjacent to plaques and at a distance, to determine whether changes in Ca2+ response were dependent upon proximity to lesions. Three parameters of the Ca2+ response were measured; initial Ca2+ peak size, plateau size and percentage of cells demonstrating oscillatory Ca2+ responses. Significance was assessed by a t-test or ANOVA (p<0.05). Sudan IV staining confirmed aortae from old ApoE-/- had clear atherosclerotic plaques, whereas those from young ApoE-/- showed either no or barely visible tiny areas of plaque (10w n=10; 24w n=9; 30w n=5). No WT mice had plaques in the aorta (10w n=10; 24w n=5; 30w n=3). Ca2+ responses (peak, plateau) in TA from 10 week WT and ApoE-/- cells were similar, except at 10μM CCh, where the response was larger in ApoE-/- (n=4-7). In AA, Ca2+ responses were significantly larger in ApoE-/- even at lower [CCh] (n=4-6). In 24 week ApoE-/- TA, responses in plaque-free regions were similar to WT, whereas those adjacent to plaque were enhanced (at 0.3 & 10μM CCh, n=3-4). In the plaque-prone AA, Ca2+ responses were significantly increased in ApoE-/- cells both adjacent to and away from lesions (n=3-4). In 30 week mice, the effect of 10μM CCh was compared (n=3-6). In plaque-free TA, Ca2+ responses were again similar to WT, but adjacent to plaques, responses were significantly increased in ApoE-/-. Plaques were so extensive in the AA that plaque-free regions were not found. Ca2+ responses were also significantly increased compared to WT. A subset of endothelial cells responds to CCh with an oscillatory Ca2+ response. In WT mice of any age, 1-2% of cells give an oscillatory Ca2+ response. In young ApoE-/- and plaque-free regions of older ApoE-/-, this is unchanged. However, a significant increase in oscillations was seen in TA and AA cells adjacent to lesions in older mice (n=5-11).ApoE-/- Ca2+ signalling is significantly altered compared to WT prior to plaque development and is accentuated as the mice age. Greater differences are seen in plaque-prone AA than in the TA and proximity to plaques enhances the changes further, including a shift towards Ca2+ oscillations.

Where applicable, experiments conform with Society ethical requirements