title: Small dense LDL enhances THP-1 macrophage foam cell formation.
abstract: OBJECTIVE
  Increased levels of small dense low-density lipoproteins (sd-LDL) have been reported more atherogenic compared to total low-density lipoprotein (LDL); however, no definitive experiments using macrophages have examined this concept in vitro.
  
  
  RESULTS
  In this study, we isolated fractions of total LDL (density 1.019-1.063 g/ml) and sd-LDL (density 1.044-1.063 g/ml) from the plasma of subjects with modest hypertriglycidemia. Oxidizabilty as assessed by copper-induced generation (1.6 µmol/L CuSO(4),12 h) of thiobarbituric acid reactive substances (TBARS) was significantly greater (7-fold higher, p < 0.01) for sd-LDL (4.3 ± 1.1 nmol/mg) than for total LDL (0.6 ± 0.2 nmol/mg) at the same cholesterol concentrations. Moreover, oxidized sd-LDL induced more lipid staining in macrophages than oxidized total LDL. When non-oxidized sd-LDL were incubated with THP1 macrophages, there was much greater lipid accumulation as assessed by oil red O staining, and more than a 2-fold increase (p < 0.05) in intracellular triglyceride content as compared to non-oxidized total LDL. Furthermore, non-oxidized sd-LDL in contrast to non-oxidized total LDL enhanced macrophage lectin-like oxidized LDL receptor-1 (LOX-1) protein expression and significantly LOX-1 mRNA levels (+158%, p < 0.05), with no effect on scavenger receptor A or CD36 gene expression. These effects of non-oxidized sd-LDL on LOX-1 gene expression were suppressed when Toll-like receptor 4 was inactivated either by RNAi or antibody.
  
  
  CONCLUSIONS
  Our data indicate for the first time that sd-LDL is much more effective in promoting macrophage triglyceride accumulation and LOX-1 gene expression than total LDL.
authors.affiliation: Life Science and Bioethics Research Center, Tokyo Medical and Dental University, Tokyo, Japan.
authors.forename: Mariko
authors.initials: M
authors.lastname: Tani
authors.forename: Akio
authors.initials: A
authors.lastname: Kawakami
authors.forename: Yuki
authors.initials: Y
authors.lastname: Mizuno
authors.forename: Reina
authors.initials: R
authors.lastname: Imase
authors.forename: Yasuki
authors.initials: Y
authors.lastname: Ito
authors.forename: Kazuo
authors.initials: K
authors.lastname: Kondo
authors.forename: Hideto
authors.initials: H
authors.lastname: Ishii
authors.forename: Masayuki
authors.initials: M
authors.lastname: Yoshida
mesh_terms: D018955:CD36 Antigens / Q000096:biosynthesis; D002460:Cell Line; D003300:Copper / Q000737:chemistry; D004305:Dose-Response Relationship, Drug; D005487:Foam Cells / Q000166:cytology*; D006801:Humans; D037102:Lectins / Q000378:metabolism; D008055:Lipids / Q000737:chemistry; D008077:Lipoproteins, LDL / Q000378:metabolism*; D008264:Macrophages / Q000166:cytology* / Q000378:metabolism; D034622:RNA Interference; D051117:Scavenger Receptors, Class A / Q000378:metabolism; D017392:Thiobarbituric Acid Reactive Substances / Q000378:metabolism; D013997:Time Factors; D051197:Toll-Like Receptor 4 / Q000378:metabolism
chemical_list: D018955:CD36 Antigens; D037102:Lectins; D008055:Lipids; D008077:Lipoproteins, LDL; D051117:Scavenger Receptors, Class A; D017392:Thiobarbituric Acid Reactive Substances; D051197:Toll-Like Receptor 4; C099252:oxidized low density lipoprotein; D003300:Copper