Vascular smooth muscle cell intracellular pst

Author

Jyotsna Muthuswamy

Date of Award

5-1997

Degree Type

Thesis

Degree Name

Master of Science

Major

Nutrition

Major Professor

Michael B. Zemel

Committee Members

Whelan, Haughton

Abstract

Exposure of cultured vascular smooth cells [VSMCs] to LDL stimulates a transient intracellular free calcium ([Ca²⁺]i) response, while in vitro oxidation of low density lipoproteins [LDL] produces marked increases in the magnitude of [Ca²⁺]i elevation compared to native LDL [N-LDL]. Increased [Ca²⁺]i exerts both trophic and contractile effects in VSMCs, and increased LDL oxidation may thereby contribute to atherosclerotic diseases. This may explain, in part, the increased atherogenicity of oxidized LDL [OX-LDL]. Complications in diabetes have been proposed to result, in part, from increased oxidative stress and OX-LDL has been demonstrated in vivo in atherosclerotic lesions. Consequently, the ability of LDL, to stimulate [Ca²⁺]i responses in cultured VSMCs, may provide a useful index of atherogenicity.

To evaluate this concept, the present study examined (i) the effect of a 12 week randomized, double-blind, placebo-controlled cross-over trial of α-tocopherol [400mg] in 12 healthy adult males, on the ability of their subsequently isolated LDL to increase [Ca²⁺]i in cultured VSMCs; and [ii] whether LDL isolated from persons with diabetes [8 type I diabetic patients] would stimulate a greater [Ca²⁺]i response in cultured VSMCs compared to healthy controls.

LDL was isolated in the presence of butylated hydroxytoluene [BHT] and the extent of oxidation was determined by quanititating thiobarbituric acid reactive substances [TEARS]. LDL 20µg from each subject then was used to stimulate fura-2 loaded rat VSMCs [10⁶ cells/ml] and [Ca²⁺]i responses were measured flourometrically.

Although in vitro OX-LDL elicited a greater [Ca²⁺]i response than N-LDL, α-tocopherol supplementation was without effect on either VSMC [Ca²⁺]i or TEARS. Thus a-tocopherol supplementation appears to have conferred no protection in healthy individuals using this ex vivo atherogenicity index. However, in patients with higher oxidative stress, as in persons with diabetes, there was a 55% increase in TEARS [P<0.0001] and an approximate four-fold increase in the [Ca²⁺]i response to their LDL compared to healthy controls [444nM vs 104nM [Ca²⁺]i response in persons with diabetes and controls, respectively; p<0.025].

Thus the ability of LDL to stimulate [Ca²⁺]i in cultured VSMCs may serve as a useful ex vivo index of atherogenicity in clinical trials as well as in patients with higher oxidative stress, such as smokers and persons with diabetes.

Recommended Citation

Muthuswamy, Jyotsna, "Vascular smooth muscle cell intracellular pst. " Master's Thesis, University of Tennessee, 1997.
https://trace.tennessee.edu/utk_gradthes/10619