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Investigation of the atherogenic potential of different human macrophage phenotypes

University of British Columbia

Atherosclerosis is the underlying cause of ischemic heart disease and strokes which accounts for the majority of cardiovascular deaths. Macrophages are one of the key cells in atherosclerotic lesions and are responsible the accumulation of lipids as well as the destabilization of plaques through the expression of proteases. Macrophages display a number of phenotypes depending on their specific environment which may affect atherosclerosis in different ways. This thesis describes the study of macrophages derived from primary human peripheral blood monocytes that were cultured and induced towards different phenotypes with combinations of interferon γ (IFNγ) and tumour necrosis factor α (TNFα), interleukin(IL)-4 and -13, or IL-10. The macrophage phenotypes were assessed for their protease and protease inhibitor profile with the use of a microarray and were also evaluated for their ability to maintain cholesterol homeostasis. Macrophages treated with IFNγ/TNFα demonstrated a trend for increased protease activation. The gene SPINT2 was found to be up-regulated by IL-4/13 treatment when compared with all other macrophage phenotypes and may serve as a marker of alternative macrophage activation. Both IFNγ and TNFα were found to decrease the amount of cholesterol accumulated when macrophages were incubated with oxidized low density lipoprotein, which may be explained by the concurrent down regulation of the macrophage scavenger receptor and CD36. IFNγ was also found to inhibit the peroxisome proliferator-activated receptor (PPAR)γ-mediated upregulation of CD36 protein by rosiglitazone without modulating PPARγ protein levels. Additionally, IL-4/13 treatment was found to increase the rate of apolipoprotein AI-mediated cholesterol efflux, yet cause a decrease in ABCA1 protein levels. The cell line U937 was then evaluated as a model of primary human macrophages to study the regulation of CD36 by IFNγ. Although IFNγ treated U937 cells showed a reduction of mature CD36 protein, they did not show an inhibition of PPARγ activity. Further studies validating the targets identified in the microarray may unveil novel proteases involved in atherosclerosis. These findings also provide insight into how different macrophage phenotypes may handle cholesterol in atherosclerotic conditions.

Text

2014-03-13

Attribution-NonCommercial-NoDerivs 2.5 Canada

http://hdl.handle.net/2429/46233

Pathology and Laboratory Medicine

University of British Columbia

UBCV

http://creativecommons.org/licenses/by-nc-nd/2.5/ca/