HDL-holoparticle uptake by alveolar type II cells: effect of vitamin E status.
Alveolar type II cells accumulate vitamin E preferentially from high-density lipoproteins (HDL) and express at least three receptors that are specific for HDL. The expression of these receptors increases in response to vitamin E deficiency. Beside receptors for specific lipid transfer from HDL, cubilin and megalin, several other receptors that mediate HDL-particle uptake were found in the lung. We hypothesize that alveolar type II cells also exhibit the HDL-particle uptake and that this process can be regulated by the vitamin E status. By confocal laser microscopy and flow cytometry we showed that type II cells accumulate protein-labeled HDL-particle. Vitamin E depletion in rats increased HDL-particle uptake in alveolar type II cells and the expression of megalin. The expression of cubilin did not change. Refeeding with vitamin E reversed HDL-particle uptake and megalin expression. Long-time incubation of type II cells with phorbol myristyl acetate (PMA) reduced HDL-holoparticle uptake and megalin expression. We assume that alveolar type II cells exhibit HDL-holoparticle uptake mediated by megalin and cubilin. Megalin represents the regulated element of the megalin/cubilin receptor-cooperation and can be modulated by protein kinase C.
Kolleck
Ingrid
I
Department of Neonatology, University Hospital Charité, Humboldt-University of Berlin, Germany.
Wissel
Heide
H
Guthmann
Florian
F
Schlame
Michael
M
Sinha
Pranav
P
Rüstow
Bernd
B
D000818:Animals; D019587:Dietary Supplements; D005434:Flow Cytometry; D005456:Fluorescent Dyes; D007700:Kinetics; D008075:Lipoproteins, HDL / Q000378:metabolism*; D026561:Low Density Lipoprotein Receptor-Related Protein-2 / Q000235:genetics / Q000378:metabolism*; D018613:Microscopy, Confocal; D010316:Particle Size; D011650:Pulmonary Alveoli / Q000166:cytology / Q000378:metabolism*; D012333:RNA, Messenger / Q000096:biosynthesis; D051381:Rats; D017208:Rats, Wistar; D011956:Receptors, Cell Surface / Q000235:genetics / Q000378:metabolism*; D013194:Staining and Labeling; D014810:Vitamin E / Q000378:metabolism*; D014811:Vitamin E Deficiency / Q000378:metabolism
D005456:Fluorescent Dyes; D008075:Lipoproteins, HDL; D026561:Low Density Lipoprotein Receptor-Related Protein-2; D012333:RNA, Messenger; D011956:Receptors, Cell Surface; C029486:intrinsic factor-cobalamin receptor; D014810:Vitamin E