title: Calcium regulation of endothelial permeability to low-density lipoprotein.
abstract: Increasing clinical and experimental evidence suggests a multifunctional role of calcium in determining the response of the arterial intima to atherogenic stimuli. In this study, an endothelial cell (EC)-smooth muscle cell (SMC) bilayer model of the arterial wall was used to investigate the effect of calcium manipulation on the sequestration of 125I-labeled LDL within the subendothelial space. Bilayer cell cultures were exposed to EGTA (0.25-2.0 mM), ionophore A23187 (5 x 10(-6) M), lanthanum chloride (0.1 mM), and trifluoperazine (TFP; 0.25 microM). The movement of 125I-labeled LDL (10 micrograms/ml) through the endothelial barrier was measured, as was the binding and cellular uptake of 125I-labeled LDL by each cell type. Extracellular Ca2+ chelation with EGTA and intracellular Ca2+ mobilization with A23187 both increased EC permeability to LDL (P < 0.05; P = 0.0001, respectively), while not significantly affecting EC binding or uptake of lipoprotein. Conversely, these agents increased SMC uptake of LDL (P < 10(-7); P < 10(-8), respectively). Calcium blockade with lanthanum chloride had the opposite effect, reducing EC permeability (P = 0.011) and SMC uptake (P < 10(-5)), while increasing EC uptake (P = 0.016). TFP, a calmodulin inhibitor, had an effect similar to A23187, although reducing SMC uptake of LDL (P = 0.015). Alteration of the calcium gradient across the plasma membrane appears to influence EC permeability. This effect may be stabilized by Ca2+ blockade or calmodulin regulation of cytoplasmic Ca2+. Additional anti-atherogenic effects of calcium blockade may include a reduction in SMC uptake by the SMC.
authors.affiliation: Department of Surgery, Case Western Reserve University, Cleveland Metropolitan General Hospital, Ohio 44109, USA.
authors.forename: J J
authors.initials: JJ
authors.lastname: Alexander
authors.forename: R
authors.initials: R
authors.lastname: Miguel
authors.forename: J J
authors.initials: JJ
authors.lastname: Piotrowski
mesh_terms: D000818:Animals; D001011:Aorta / Q000166:cytology / Q000378:metabolism; D000001:Calcimycin / Q000494:pharmacology; D002118:Calcium / Q000037:antagonists & inhibitors / Q000502:physiology*; D002147:Calmodulin / Q000037:antagonists & inhibitors; D002417:Cattle; D002452:Cell Count; D002463:Cell Membrane Permeability / Q000502:physiology; D004533:Egtazic Acid / Q000494:pharmacology; D004730:Endothelium, Vascular / Q000166:cytology* / Q000378:metabolism; D007811:Lanthanum / Q000494:pharmacology; D008077:Lipoproteins, LDL / Q000378:metabolism*; D009000:Monocytes / Q000166:cytology; D009130:Muscle, Smooth / Q000166:cytology / Q000378:metabolism; D014268:Trifluoperazine / Q000494:pharmacology
chemical_list: D002147:Calmodulin; D008077:Lipoproteins, LDL; C028521:lanthanum chloride; D014268:Trifluoperazine; D000001:Calcimycin; D004533:Egtazic Acid; D007811:Lanthanum; D002118:Calcium