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Lipoprotein Lipase regulates the expression of genes responsible for cellular cholesterol uptake and efflux in human and mouse macrophages.
Author(s) -
Moctar Khadija,
Madhwani Kimberly Rose R.,
Kim Aidan J.M,
Medh Jheem D.
Publication year - 2017
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.31.1_supplement.629.10
Subject(s) - scavenger receptor , cd36 , lipoprotein lipase , abca1 , foam cell , macrophage , atp binding cassette transporter 1 , efflux , receptor , cholesterol , biology , chemistry , lipid raft , biochemistry , microbiology and biotechnology , lipoprotein , transporter , adipose tissue , gene , in vitro
Background Cellular cholesterol accumulation is the net result of receptor‐mediated cellular uptake and transporter‐mediated efflux. Scavenger receptors (CD36, SR‐AI, SR‐BI) mediate the cellular uptake of cholesterol whereas the ATP‐binding cassette transporter A1 (ABCA1) mediates the unidirectional efflux of excess cholesterol. SR‐BI also mediates bidirectional cholesterol transport. Lipoprotein lipase (LPL) is secreted by macrophages and catalyzes the hydrolysis of circulating triglycerides. Macrophage LPL expression was shown to be inversely correlated with ABCA1 levels. We hypothesized that LPL may regulate the expression of macrophage scavenger receptors as well. Objective To examine if the expression of macrophage scavenger receptors and cholesterol transporter are regulated by LPL. Regulation of gene expression was studied in LPL‐knock‐down THP‐1 macrophages and LPL‐over‐expressing mouse macrophages. Additionally we are preparing recombinant wild type and mutant LPL to determine which structural components of LPL modulate cholesterol efflux. Methods THP‐1 monocytes were cultured and were induced to differentiate into macrophages with phorbol 12‐myristate 13‐acetate. Thioglycolate‐stimulated macrophages were isolated from the peritoneal cavity of transgenic mice with macrophage‐specific LPL overexpression. The expression of CD36, SR‐AI, SR‐BI and ABCA1 was compared in normal and LPL‐(THP‐1) or LPL+ (mice) macrophages by RT‐PCR analysis. b‐actin served as a control for RNA mass. Gel images were quantified by ImageJ analysis. Results Silencing of the LPL gene in THP‐1 macrophages correlated with a significant increase in ABCA1 expression (161% of WT). This was corroborated in mouse macrophages since overexpression of LPL resulted in a 50% decrease in ABCA1 expression. The expression of scavenger receptors SR‐BI and CD36 was significantly lower in LPL‐THP‐1 cells compared to WT macrophages (55% and 60%, respectively, compared to WT). Contrary to results in THP‐1 cells, LPL‐overexpressing mouse macrophages showed a decrease in SR‐BI levels (20% of WT), but no change in CD36 expression. The expression of SR‐AI was not influenced by LPL silencing or overexpression. Conclusion Manipulation of LPL expression modulates the transcription of genes relevant to cholesterol accumulation in isolated THP‐1 cells. In LPL+ transgenic mice, a decrease in SR‐BI may be due to the influence of other organs in cholesterol homeostasis and SR‐BI's role in cholesterol efflux. Support or Funding Information Acknowledgements: This work was supported by National Institutes of Health Awards R15HL083946, SC3GM095413, GM008395 and GM063787.