Apolipoprotein D inhibits platelet-derived growth factor-BB-induced vascular smooth muscle cell proliferated by preventing translocation of phosphorylated extracellular signal regulated kinase 1/2 to the nucleus.
OBJECTIVE
Elevated apolipoprotein D (apoD) levels are associated with reduced proliferation of cancer cells. We therefore investigated whether apoD, which occurs free or associated with HDL, suppresses vascular smooth muscle cell (VSMC) proliferation, which is related to the pathobiology of disease.


RESULTS
Intense immunoreactivity for apoD was observed in human atherosclerotic plaque but not in normal coronary artery. However, an increase in apoD mRNA was seen in quiescent relative to proliferating fetal lamb aortic VSMCs, and in the rat aortic VSMC line (A10), we demonstrated uptake of apoD from serum. Stable transfection of apoD in A10 cells in the absence of serum did not influence VSMC proliferation assessed by [3H]-thymidine incorporation. ApoD, administered at a dose of 100 ng/mL, completely inhibited basal as well as platelet-derived growth factor (PDGF)-BB-induced VSMC proliferation (P<0.01) but had no effect on fibroblast growth factor-induced VSMC proliferation. ApoD did not suppress PDGF-BB or fibroblast growth factor-2-induced phosphorylation of extracellular signal regulated kinase (ERK) 1/2 but selectively inhibited PDGF-BB-mediated ERK1/2 nuclear translocation.


CONCLUSIONS
Our data suggest that apoD selectively modulates the proliferative response of VSMC to growth factors by a mechanism related to nuclear translocation of ERK1/2.
Sarjeant
Jennifer M
JM
Cardiovascular Research Program, The Hospital for Sick Children, and the Department of Pediatrics, University of Toronto.
Lawrie
Allan
A
Kinnear
Caroline
C
Yablonsky
Shmuel
S
Leung
Wesley
W
Massaeli
Hamid
H
Prichett
Wendy
W
Veinot
John P
JP
Rassart
Eric
E
Rabinovitch
Marlene
M
D000818:Animals; D001011:Aorta; D001053:Apolipoproteins / Q000096:biosynthesis / Q000235:genetics / Q000494:pharmacology / Q000502:physiology*; D053399:Apolipoproteins D; D001161:Arteriosclerosis / Q000378:metabolism; D000077214:Becaplermin; D002455:Cell Division / Q000187:drug effects / Q000235:genetics / Q000502:physiology; D002478:Cells, Cultured; D003331:Coronary Vessels / Q000737:chemistry / Q000473:pathology / Q000502:physiology; D019950:Mitogen-Activated Protein Kinase 1 / Q000378:metabolism*; D048052:Mitogen-Activated Protein Kinase 3; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism*; D009131:Muscle, Smooth, Vascular / Q000737:chemistry / Q000187:drug effects / Q000201:enzymology / Q000378:metabolism*; D010766:Phosphorylation / Q000187:drug effects; D010982:Platelet-Derived Growth Factor / Q000037:antagonists & inhibitors* / Q000502:physiology*; D021381:Protein Transport / Q000187:drug effects / Q000502:physiology; D020574:Proto-Oncogene Proteins c-sis; D012333:RNA, Messenger / Q000096:biosynthesis / Q000378:metabolism; D051381:Rats; D012756:Sheep; D014162:Transfection
D001053:Apolipoproteins; D053399:Apolipoproteins D; D010982:Platelet-Derived Growth Factor; D020574:Proto-Oncogene Proteins c-sis; D012333:RNA, Messenger; D000077214:Becaplermin; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3; D020928:Mitogen-Activated Protein Kinases