Scavenger receptor class B, type I is expressed in porcine brain capillary endothelial cells and contributes to selective uptake of HDL-associated vitamin E

J Neurochem. 2001 Jan;76(2):498-508. doi: 10.1046/j.1471-4159.2001.00100.x.


It is clearly established that an efficient supply to the brain of alpha-tocopherol (alphaTocH), the most biologically active member of the vitamin E family, is of the utmost importance for proper neurological functioning. Although the mechanism of uptake of alphaTocH into cells constituting the blood-brain barrier (BBB) is obscure, we previously demonstrated that high-density lipoprotein (HDL) plays a major role in the supply of alphaTocH to porcine brain capillary endothelial cells (pBCECs). Here we studied whether a porcine analogue of human and rodent scavenger receptor class B, type I mediates selective (without concomitant lipoprotein particle internalization) uptake of HDL-associated alphaTocH in a similar manner to that described for HDL-associated cholesteryl esters (CEs). In agreement with this hypothesis we observed that a major proportion of alphaTocH uptake by pBCECs occurred by selective uptake, exceeding HDL3 holoparticle uptake by up to 13-fold. The observation that selective uptake of HDL-associated CE exceeded HDL3 holoparticle up to fourfold suggested that a porcine analogue of SR-BI (pSR-BI) may be involved in lipid uptake at the BBB. In line with the observation of selective lipid uptake, RT-PCR and northern and western blot analyses revealed the presence of pSR-BI in cells constituting the BBB. Adenovirus-mediated overexpression of the human analogue of SR-BI (hSR-BI) in pBCECs resulted in a fourfold increase in selective HDL-associated alphaTocH uptake. In accordance with the proposed function of SR-BI, selective HDL-CE uptake was increased sixfold in Chinese hamster ovary cells stably transfected with murine SR-BI (mSR-BI). Most importantly stable mSR-BI overexpression mediated a twofold increase in HDL-associated [14C]alphaTocH selective uptake in comparison with control cells. In line with tracer experiments, mass transfer studies with unlabelled lipoproteins revealed that mSR-BI overexpression resulted in a twofold increase in endogenous HDL3-associated alphaTocH uptake. The results of this study indicate that SR-BI promotes the uptake of HDL-associated alphaTocH into cells constituting the BBB and plays an important role during the supply of the CNS with this indispensable micronutrient.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Animals
  • Blood-Brain Barrier / physiology
  • Brain / blood supply
  • CD36 Antigens / biosynthesis*
  • CD36 Antigens / genetics
  • CHO Cells
  • Capillaries / cytology
  • Capillaries / metabolism*
  • Cells, Cultured
  • Cricetinae
  • Endothelium, Vascular / cytology
  • Endothelium, Vascular / metabolism*
  • Lipoproteins, HDL / metabolism*
  • Lipoproteins, HDL3
  • Membrane Proteins*
  • Receptors, Immunologic*
  • Receptors, Lipoprotein*
  • Receptors, Scavenger
  • Scavenger Receptors, Class B
  • Swine
  • Transfection
  • Vitamin E / metabolism
  • Vitamin E / pharmacokinetics*


  • CD36 Antigens
  • Lipoproteins, HDL
  • Lipoproteins, HDL3
  • Membrane Proteins
  • Receptors, Immunologic
  • Receptors, Lipoprotein
  • Receptors, Scavenger
  • Scarb1 protein, mouse
  • Scavenger Receptors, Class B
  • Vitamin E