Altered Ca2+ handling of smooth muscle cells in aorta of apolipoprotein E-deficient mice before development of atherosclerotic lesions.
To study the effect of hypercholesterolemia on vascular smooth muscle cell (VSMC) function, atherosclerosis-prone but plaque-free endothelium-denuded aortic rings (width 2mm) from C57Bl6 Wild Type (WT) and apolipoprotein E-deficient (apoE(-/-)) mice (age 4 months) were mounted in a myograph and loaded with Fura-2 AM to simultaneously measure free Ca(2+) ([Ca(2+)](i)) and force development. In comparison with WT, apoE(-/-) mice displayed higher basal [Ca(2+)](i). Moreover, the time constant of the second phase of the biphasic high K(+)-induced [Ca(2+)](i) response was significantly increased in apoE(-/-) compared to WT mice. This phase was abolished by treatment with cyclopiazonic acid (CPA), depleting sarcoplasmic reticulum (SR). Further investigation of SR dependent [Ca(2+)](i) handling with CPA and caffeine revealed no alteration of maximal SERCA or ryanodine receptor function. Inositol (1,4,5)-triphosphate receptor (IP(3)R)-mediated [Ca(2+)](i) release was, however, significantly increased in apoE(-/-) mice compared to WT mice as established with phenylephrine and ATP. In Ca(2+)-free conditions the ATP-induced [Ca(2+)](i) was not altered. The ATP-induced store-operated Ca(2+) entry was, however, significantly increased in apoE(-/-) compared to WT mice. The results demonstrate that basal [Ca(2+)](i) levels and IP(3)R-mediated store-operated [Ca(2+)](i) release over the plasma membrane were elevated in hypercholesterolemic but plaque-free apoE(-/-) mice.
Van Assche
T
T
Division of Pharmacology, University of Antwerp, CDE, T2.17, Universiteitsplein, 1, 2610-Wilrijk, Antwerpen, Belgium. tim.vanassche@ua.ac.be <tim.vanassche@ua.ac.be>
Fransen
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P
Guns
P-J
PJ
Herman
A G
AG
Bult
H
H
D000255:Adenosine Triphosphate / Q000494:pharmacology; D000818:Animals; D001011:Aorta / Q000378:metabolism; D001057:Apolipoproteins E / Q000172:deficiency*; D050197:Atherosclerosis / Q000235:genetics / Q000378:metabolism / Q000473:pathology; D002118:Calcium / Q000378:metabolism*; D020013:Calcium Signaling; D004791:Enzyme Inhibitors / Q000494:pharmacology; D006937:Hypercholesterolemia / Q000235:genetics / Q000378:metabolism* / Q000473:pathology; D007211:Indoles / Q000494:pharmacology; D053496:Inositol 1,4,5-Trisphosphate Receptors / Q000378:metabolism; D051379:Mice; D009131:Muscle, Smooth, Vascular / Q000378:metabolism* / Q000473:pathology; D011188:Potassium / Q000378:metabolism; D019837:Ryanodine Receptor Calcium Release Channel / Q000378:metabolism; D012519:Sarcoplasmic Reticulum / Q000378:metabolism / Q000473:pathology; D053498:Sarcoplasmic Reticulum Calcium-Transporting ATPases / Q000378:metabolism
D001057:Apolipoproteins E; D004791:Enzyme Inhibitors; D007211:Indoles; D053496:Inositol 1,4,5-Trisphosphate Receptors; D019837:Ryanodine Receptor Calcium Release Channel; D000255:Adenosine Triphosphate; D053498:Sarcoplasmic Reticulum Calcium-Transporting ATPases; D011188:Potassium; D002118:Calcium; C000543:cyclopiazonic acid