Induction of monocyte differentiation and foam cell formation in vitro by 7-ketocholesterol

Abstract

Oxidized LDL (OxLDL) is composed of many potentially proatherogenic molecules, including oxysterols. Of the oxysterols, 7-ketocholesterol (7-KC) is found in relatively large abundance in OxLDL, as well as in atherosclerotic plaque and foam cells in vivo. Although there is evidence that 7-KC activates endothelial cells, its effect on monocytes is unknown. We tested the hypothesis that 7-KC may induce monocyte differentiation and promote foam cell formation. THP-1 cells were used as a monocyte model system and were treated with 7-KC over a range of concentrations from 0.5 to 10 g/ml. Changes in cell adhesion properties, cell morphology, and expression of antigens characteristic of differentiated macrophages were monitored over a 7-day period. 7-KC promoted cells to firmly adhere and display morphologic features of differentiated macrophages; this effect was time and dose dependent and was markedly more potent than cholesterol treatment (45% of cells became adherent after 7 days of treatment with 7-KC at 10 g/ml vs. less then 5% for control cells, P Ͻ 0.01). Similar effects were obtained when LDL enriched with 7-KC or OxLDL were added to THP-1 cells. 7-KCdifferentiated cells expressed CD11b, CD36, and CD68, phagocytized latex beads, and formed lipid-laden foam cells after exposure to acetylated LDL or OxLDL. In contrast to 7-KC, oxysterols with known cell regulatory effects such as 25-hydroxycholesterol, 7 ␤ -hydroxycholesterol, and (22 R )-hydroxycholesterol did not effectively promote THP-1 differentiation. In conclusion, these results demonstrate for the first time that 7-KC, a prominent oxysterol formed in OxLDL by peroxidation of cholesterol, may play an important role in promoting monocyte differentiation and foam cell formation. These studies also suggest that 7-KC induces monocyte differentiation through a sterol-mediated regulatory pathway that remains to be characterized.

Genome-Wide Transcriptomic Analysis Identifies Pathways Regulated by Sterculic Acid in Retinal Pigmented Epithelium Cells

“…We decided to study the effects and mechanisms of action of SA in cells of retinal origin because of the potential therapeutic role of SA in ocular diseases [12,13,24]. We used a primary immortalized RPE cell line that recapitulates well RPE function and physiology [57,58], as well as ARPE19 and RF6/A cell lines to show lack of toxicity of SA up to 20 µM, which is a higher dose than the one used in vitro and in vivo to show effects [11][12][13]15,16,24,42]. These data were in agreement with reports showing the lack of toxicity in vivo, in hamsters or rats fed with an SO-enriched diet [27,41] or in vitro in differentiated adipocytes [34].…”

“…These deposits are composed of proteins, mineral and lipids [10], one which, 7-ketocholesterol (7KCh), is a central component associated with AMD pathology [11]. 7KCh is an oxysterol that has been related to several degenerative diseases, including AMD [12][13][14], atherosclerosis [15][16][17][18], Parkinson's [19,20] and Alzheimer's disease [21][22][23]. It has been demonstrated that 7KCh promotes an inflammatory and a cytotoxic response [14,24,25], but it also promotes cell arrest and cell death by different molecular mechanisms still not completely decoded [25].…”

Role of the Scavenger Receptor CD36 in Accelerated Diabetic Atherosclerosis

“…Serum oxidized sterols (oxysterols) are a major component in oxidized LDL and are thought to mediate its lipotoxic effects. Oxysterols, such as 7-ketocholesterol (7-KC), are abundant in advanced atherosclerotic lesions [28]. Therefore, we measured the levels of free 7-KC levels in the plasma of subjects and observed that circulating 7-KC levels were significantly higher in subjects with diabetes compared to subjects without diabetes (Figure 6D).…”

Dietary cholesterol oxidation products: Perspectives linking food processing and storage with health implications

“…The migration and proliferation of smooth muscle cells are induced by growth factors (Guardiola et al., 1996). Oxidized low‐density lipoprotein (oxLDLs) that stimulate monocyte differentiation lead to the generation of foam cells, the proliferation of smooth muscle cells, production of elastin and collagen, and deposition of calcium (Guardiola et al., 1996; Hayden et al., 2002). These factors together trigger the formation of atherosclerotic plaques, which gradually narrow vessel lumen and thus cause thrombosis, eventually leading to heart attack and stroke (Chisolm & Steinberg, 2000).…”