Endotoxin contamination of apolipoprotein A-I: Effect on macrophage proliferation – A cautionary tale

Abstract This technical report addresses the problem of endotoxin contamination of apolipoprotein reagents. Using a bromodeoxyuridine incorporation cell proliferation assay, we observed that human plasma ApoA-I as low as 1 μg/ml resulted in a >90% inhibition in macrophage proliferation. However,...

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Bibliographic Details
Published in:Atherosclerosis 2015-05, Vol.240 (1), p.121-124
Main Authors: Jin, Xueting, Xu, Qing, Champion, Keith, Kruth, Howard S
Format: Article
Language:English
Subjects:
Apolipoprotein A-I - analysis
Apolipoprotein A-I - pharmacology
Apolipoproteins
Atherosclerosis
Cardiovascular
Cell proliferation
Cell Proliferation - drug effects
Cells, Cultured
Dose-Response Relationship, Drug
Drug Contamination
Endotoxin
Endotoxins - analysis
Endotoxins - pharmacology
Humans
Macrophage Activation - drug effects
Macrophages
Macrophages - drug effects
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Summary:Abstract This technical report addresses the problem of endotoxin contamination of apolipoprotein reagents. Using a bromodeoxyuridine incorporation cell proliferation assay, we observed that human plasma ApoA-I as low as 1 μg/ml resulted in a >90% inhibition in macrophage proliferation. However, not all ApoA-I from different sources showed this effect. We considered the possibility that endotoxin contamination of the apolipoproteins contributed to the differential inhibition of macrophage cell proliferation. Endotoxin alone very potently inhibited macrophage proliferation (0.1 ng/ml inhibited macrophage proliferation >90%). Measurement of endotoxin levels in the apolipoprotein products, including an analysis of free versus total endotoxin, the latter which included endotoxin that was masked due to binding to protein, suggested that free endotoxin mediated inhibition of macrophage proliferation. Despite the use of an advanced endotoxin removal procedure and agents commonly used to inhibit endotoxin action, the potency of endotoxin precluded successful elimination of endotoxin effect. Our findings show that endotoxin contamination can significantly influence apparent apolipoprotein-mediated cell effects (or effects of any other biological products), especially when these products are tested on highly endotoxin-sensitive cells, such as macrophages.
ISSN:0021-9150
1879-1484
DOI:10.1016/j.atherosclerosis.2015.03.007