RCMI International Symposium on Health Disparities
November 12-15, 2000
San Juan, Puerto Rico

Oral Presentations

EFFECTS OF OXIDIZED LDL ON NITRIC OXIDE SYNTHETASE AND PROTEIN KINASE C ACTIVITIES ON BOVINE ENDOTHELIAL CELLS

Shyamali Mukherjee1,2, Sonya Denise Coaxum 2, Mohammad Maleque2 and Salil K. Das1. Department of Biochemistry 1 / Pharmacology 2 , Meharry Medical College, Nashville, TN 37208.

Endothelial dysfunction has been implicated as one of the earliest manifestation of atherosclerosis. Oxidized lipoprotein (ox-LDL) is an atherogenic lipoprotein which has been detected in atherosclerotic lesions of animals and humans. It has been suggested that ox-LDL causes endothelial dysfunction by decreasing the release of endothelium-Derived factors (EDRF) or increasing the inactivation of EDRF. The mechanism by which ox-LDL causes dysfunctional EDRF during early stages of atherosclerosis is not clear. The purpose of this study was to examine the role of ox-LDL on nitric oxide synthetase (NOS) and protein kinase C (PKC) activity in bovine aortic endothelial cells (BAEC). BAEC cells were incubated with different concentrations (25-100 ug/ml) of ox-LDL and native-LDL for 24hr. The incubation was terminated by aspiration of medium and washed twice with cold phosphate buffer saline and then cells were scraped in PBS containing EDTA with a rubber policeman and transferred to polypropylene centrifuge tube. After centrifugation, cells were suspended to respective sample buffer. NOS, PKC and protein content were determined by using commercial kits. Ox-LDL significantly stimulated PKC activity of BAEC whereas it inhibited NOS activity. Effects of ox-LDL on both NOS and PKC are dose dependent. Our results suggest that ox-LDL is likely to impair NOS activity i.e. impair endothelium-dependent relaxation by activation of PKC activity, as a result endothelial dysfunction. One possible mechanism by which ox-LDL may contribute to endothelial dysfunction is by inhibiting Gi protein function, since PKC activity has been shown to alter Gi protein function. (Supported by Grants from Army and NIH).