Oxidized LDL can promote human monocyte survival.

Abstract

To the Editor: It is likely that in the early stages of atherosclerosis, circulating monocytes migrate into the subendothelial space, where they can mature into foam cells.1 2 3 4 5 There is in vivo and in vitro evidence for both foam cell death but also enhanced survival and growth.6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 Human peripheral blood monocytes (≥95% pure) were obtained by countercurrent elutriation and usually cultured in minimal essential medium, α-modification (α-MEM)/1% pooled normal human serum (HS).23 24 The number of viable cells was measured by scraping the tissue culture surface and counting them in a hemocytometer with trypan blue exclusion or by propidium iodide staining (flow cytometry). Oxidized LDL (ox-LDL) was prepared as before.14 The number of viable monocytes declined when they were left untreated or treated with native LDL; this loss was reduced by both ox-LDL and acetylated LDL (ac-LDL; see the Table⇓). A dose response for the ox-LDL effect is provided in the online Figure⇓ (please see http://atvb.ahajournals.org) and, as we found before with murine macrophages,14 doses of ox-LDL ≤50 μg/mL generally promoted survival; at these survival-inducing doses, the cells spread on the tissue …