Scavenger receptor B1, the HDL receptor, is expressed abundantly in liver sinusoidal endothelial cells

Sci Rep. 2016 Feb 11;6:20646. doi: 10.1038/srep20646.

Abstract

Cholesterol from peripheral tissue, carried by HDL, is metabolized in the liver after uptake by the HDL receptor, SR-B1. Hepatocytes have long been considered the only liver cells expressing SR-B1; however, in this study we describe two disparate immunofluorescence (IF) experiments that suggest otherwise. Using high-resolution confocal microscopy employing ultrathin (120 nm) sections of mouse liver, improving z-axis resolution, we identified the liver sinusoidal endothelial cells (LSEC), marked by FcγRIIb, as the cell within the liver expressing abundant SR-B1. In contrast, the hepatocyte, identified with β-catenin, expressed considerably weaker levels, although optical resolution of SR-B1 was inadequate. Thus, we moved to a different IF strategy, first separating dissociated liver cells by gradient centrifugation into two portions, hepatocytes (parenchymal cells) and LSEC (non-parenchymal cells). Characterizing both portions for the cellular expression of SR-B1 by flow cytometry, we found that LSEC expressed considerable amounts of SR-B1 while in hepatocytes SR-B1 expression was barely perceptible. Assessing mRNA of SR-B1 by real time PCR we found messenger expression in LSEC to be about 5 times higher than in hepatocytes.

Publication types

  • Research Support, N.I.H., Extramural

MeSH terms

  • Animals
  • Biological Transport
  • COS Cells
  • Cell Line
  • Cell Separation
  • Chlorocebus aethiops
  • Cholesterol / metabolism*
  • Endothelial Cells / cytology
  • Endothelial Cells / metabolism*
  • Hepatocytes / cytology
  • Hepatocytes / metabolism*
  • Liver / cytology
  • Liver / metabolism*
  • Macrophages / cytology
  • Macrophages / metabolism
  • Male
  • Mice
  • Mice, Inbred BALB C
  • Mice, Inbred C57BL
  • Mice, Knockout
  • Microscopy, Confocal
  • Microtomy
  • Organ Specificity
  • RNA, Messenger / genetics*
  • RNA, Messenger / metabolism
  • Receptors, IgG / genetics
  • Receptors, IgG / metabolism
  • Scavenger Receptors, Class B / genetics*
  • Scavenger Receptors, Class B / metabolism
  • beta Catenin / genetics
  • beta Catenin / metabolism

Substances

  • CTNNB1 protein, mouse
  • Fcgr2b protein, mouse
  • RNA, Messenger
  • Receptors, IgG
  • Scarb1 protein, mouse
  • Scavenger Receptors, Class B
  • beta Catenin
  • Cholesterol