טכניון מכון טכנולוגי לישראל
הטכניון מכון טכנולוגי לישראל - בית הספר ללימודי מוסמכים  
M.Sc Thesis
M.Sc StudentRozenberg Orit
SubjectThe Effect of Paraoxonase (PON1) on Macrophage Oxidative
Status and Cholesterol Biosynthesis
DepartmentDepartment of Medicine
Supervisor Professor Emeritus Michael Aviram


Abstract

Human serum paraoxonase (PON1) is an esterase whose activity is inversely related to the atherosclerotic lesion development, which contains cholesterol-loaded macrophage foam cells. The aim of the present study was to examine whether the anti-atherogenic properties of PON1 are related to its capacity to reduce oxidative stress and cholesterol biosynthesis in macrophages. For this purpose we used mouse peritoneal macrophages (MPM) harvested from PON1-deficient and from control mice. PON1-deficient mice exhibited a significantly 51% increased atherosclerotic lesion area and a 35% higher macrophage cholesterol content, compared to control mice. Macrophage lipid peroxides content and macrophage capacity to oxidize LDL were increased in PON1-deficient mice MPM, compared control mice MPM. Moreover, increased release of macrophage superoxide anion from PON1-deficient MPM as well as increased activation of the NADPH oxidase enzyme were noticed. Furthermore, purified human PON1 was found to directly decrease, peroxides content (by 18%), macrophage superoxide anion release (by 33%) and macrophage-mediated oxidation of LDL (by 22%) in PON1-deficient mice MPM.

We found that the macrophage cholesterol biosynthesis was increased in MPM from PON1-deficient mice by 50%, compared to their controls. Human PON1 resulted in a dose-dependent decrease (40% - 84%) in macrophage cholesterol biosynthesis in MPM from PON1-deficient and control mice. We observed a PON1 phospholipase-A2-like activity on MPM, as evidenced by formation of lysophosphatidylcholine. Upon incubation of macrophages with lysophosphatidylcholine, a dose-dependent inhibition of cellular cholesterol biosynthesis was noted. We thus concluded that PON1-deficiency results in increased macrophage oxidative stress and macrophage cholesterol biosynthesis in PON1-deficient mice, and that PON1 can also directly decreases macrophage oxidative stress and cholesterol biosynthesis, major processes that induce foam cell formation and atherosclerosis progression.