Project Details


The overall aim of the proposed studies is to achieve a better
understanding of the regulation of apoE expression in tissue macrophages by
physiological stimuli, such as HDL or endotoxin. Specifically, the
hypothesis that second messengers of the cAMP- dependent protein kinase and
protein kinase C pathways are involved in the positive and negative
regulation of apoE secretion and synthesis by HDL or endotoxin,
respectively, will be examined in cholesterol- loaded mouse peritoneal,
thioglycolate- elicited macrophages.

The role of adenylate cyclase in mediating the stimulation of apoE
secretion by HDL will be examined in cell cultures. The mechanism of
adenylate cyclase activation by HDL through GTP- binding proteins will be
examined in detail in macrophage membrane preparations, using both,
biochemical and immunological techniques.

The second portion of the proposed work is aimed at elucidating the
mechanism of endotoxin-mediated suppression of apoE synthesis and secretion
through activation of protein kinase C. The effects of phorbol ester,
endotoxin and exogenous phospholipase C on macrophage protein kinase C
activities, IP3 generation and cytosolic C++ accumulation will be
correlated to changes in rates of apoE synthesis and secretion in cultured
macrophages. The apparent, protein kinase C- mediated translational
regulation of apoE synthesis will be examined by in vitro translation
assays. The extent of apoE synthesis and secretion by cultured cells or in
translation assays will be determined by immunoprecipitation.

The proposed studies will provide insight into the process of reverse
cholesterol transport and further our understanding of the protective role
HDL in the development of atherosclerosis. Useful information about the
mechanisms of endotoxin-induced hyperlipidemia and regulation of immune
response will also be obtained. These studies will be the foundation of
future studies on the interaction of the two signalling pathways in the
regulation of apoE expression.
Effective start/end date1/08/9131/07/92