Plant sterols increased IL-6 and TNF-α secretion from macrophages, but to a lesser extent than cholesterol.
OBJECTIVE
Phytosterolemia is an inherited disorder characterized by hypercholesterolemia and premature atherosclerosis, together with increased inflammatory states in some cases. The underlying mechanisms of atherogenesis in phytosterolemia, however, have not been completely elucidated. In this study, we investigated whether phytosterols would affect inflammatory reactions in macrophages and macrophage cell lines.


METHODS
We incubated RAW264.7 cells (RAW) and mouse peritoneal macrophages (MPMs) with sitosterol (Sito), campesterol (Camp) or cholesterol (Chol) at low (8 µM, 16 µM) or high (160 µM) concentrations, and investigated their effects on LPS-induced secretion of IL-6 and TNF-α. We also analyzed their effects on endoplasmic reticulum (ER) stress in both cells, and on the cell proliferation of RAW.


RESULTS
At low sterol concentrations, only Chol resulted in a tendency toward the increased secretion of TNF-α from MPMs. At high concentrations, Chol induced a significant increase in TNF-α secretions from both cells; however, Sito resulted in a non-significant increase in TNF-α secretion. The effects on IL-6 secretions of Sito were also significantly less than those of Chol. Camp increased the secretions of both cytokines from MPMs; however, the extent of these increases was less pronounced than that of Chol. Augmentation of ER stress was greatest with Chol among the sterols, and the proliferation of RAW cells was inhibited only with Chol.


CONCLUSIONS
The lesser degree of inflammatory reactions and toxicity in macrophages with phytosterols than with cholesterol suggests that plant sterols themselves might not be primarily responsible for atherogenesis in phytosterolemia.
Department of Metabolic Diseases, Graduate School of Medicine, The University of Tokyo, Japan.
Makoto
M
Kurano
Naoyuki
N
Iso-O
Masumi
M
Hara
Eisei
E
Noiri
Kazuhiko
K
Koike
Takashi
T
Kadowaki
Kazuhisa
K
Tsukamoto
D017398:Alternative Splicing; D000818:Animals; D049109:Cell Proliferation / Q000187:drug effects; D002478:Cells, Cultured; D002784:Cholesterol / Q000031:analogs & derivatives* / Q000494:pharmacology*; D004268:DNA-Binding Proteins / Q000235:genetics; D004721:Endoplasmic Reticulum / Q000187:drug effects / Q000378:metabolism; D006937:Hypercholesterolemia; D015850:Interleukin-6 / Q000378:metabolism*; D007410:Intestinal Diseases; D008052:Lipid Metabolism, Inborn Errors; D008070:Lipopolysaccharides / Q000494:pharmacology; D008262:Macrophage Activation / Q000187:drug effects; D008264:Macrophages / Q000187:drug effects* / Q000378:metabolism; D051379:Mice; D010840:Phytosterols / Q000009:adverse effects / Q000494:pharmacology*; D000071701:Regulatory Factor X Transcription Factors; D014157:Transcription Factors / Q000235:genetics; D014409:Tumor Necrosis Factor-alpha / Q000378:metabolism*
D004268:DNA-Binding Proteins; D015850:Interleukin-6; D008070:Lipopolysaccharides; D010840:Phytosterols; D000071701:Regulatory Factor X Transcription Factors; D014157:Transcription Factors; D014409:Tumor Necrosis Factor-alpha; C021273:campesterol; D002784:Cholesterol