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Dissertation/Thesis Abstract

Inhibition of the cholesterol biosynthetic pathway modulates the innate immune response
by Frey, Tiffany Albright, Ph.D., The Johns Hopkins University, 2009, 167; 3340038
Abstract (Summary)

Sepsis, which is the product of a poorly controlled inflammatory response, is a major health problem in the United States. There is not adequate therapy for sepsis and patient care is mainly supportive. Human clinical studies have indicated that statins, which are widely used for the treatment of hypercholesterolemia, may be beneficial in sepsis. We investigated the effect of statins on macrophage (M&phis;) CD14 expression. CD14 is the major binding site for bacterial lipopolysaccharide (LPS), which is an important mediator of gram-negative sepsis. This glycoprotein is found in both a membrane-bound form on the cell surface (mCD14) and in a soluble variant in circulation (sCD14). Treatment of RAW 264.7 M&phis;s with lovastatin resulted in elevated mCD14 levels and decreased sCD14 levels following LPS stimulation. The increase in mCD14 was dependent on depletion of the isoprenoid intermediate geranylgeranylpyrophosphate (GGPP) and subsequent inhibition of Rho GTPases, whereas the effect of lovastatin on sCD14 was not dependent on GGPP depletion alone. While increased mCD14 expression in the presence of lovastatin correlated with increased tumor necrosis factor (TNF) -α secretion, decreased release of sCD14 may result in a diminished systemic response to LPS and therefore provide a benefit to septic patients.

Another inhibitor of cholesterol biosynthesis is itraconazole (ICZ), which blocks the pathway downstream of the isoprenoid intermediates, acting on lanosterol 14-α demethylase. ICZ altered both the expression and glycosylation of CD14 in RAW 264.7 M&phis;s. The effect of ICZ on glycosylation was not due to trafficking since the protein was delivered to the cell surface and released as the soluble variant. Moreover, the alternately glycosylated form of CD14 appears to be functional as indicated by increased LPS-induced TNF-α release at a CD14-specific concentration of LPS. Metabolic labeling with [2-3H]-mannose revealed that no glycoproteins with complex-modified N-glycans are being made in the presence of ICZ. This effect is not likely to be dependent on inhibition of the cholesterol biosynthetic pathway since other azole antifungals that block the cholesterol pathway did not affect glycosylation. Therefore, alterations in the glycosylation process are a novel effect of ICZ on macrophages that may have consequences for immune function.

Indexing (document details)
Advisor: Maio, Antonio De
School: The Johns Hopkins University
School Location: United States -- Maryland
Source: DAI-B 69/12, Dissertation Abstracts International
Subjects: Cellular biology
Keywords: Cholesterol, Glycosylation, Innate immunity, Lipopolysaccharide, Macrophages, Sepsis
Publication Number: 3340038
ISBN: 978-0-549-94016-6
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