Activation of nuclear receptor Nur77 by 6-mercaptopurine protects against neointima formation.
BACKGROUND
Restenosis is a common complication after percutaneous coronary interventions and is characterized by excessive proliferation of vascular smooth muscle cells (SMCs). We have shown that the nuclear receptor Nur77 protects against SMC-rich lesion formation, and it has been demonstrated that 6-mercaptopurine (6-MP) enhances Nur77 activity. We hypothesized that 6-MP inhibits neointima formation through activation of Nur77.


RESULTS
It is demonstrated that 6-MP increases Nur77 activity in cultured SMCs, which results in reduced [3H]thymidine incorporation, whereas Nur77 small interfering RNA knockdown partially restores DNA synthesis. Furthermore, we studied the effect of 6-MP in a murine model of cuff-induced neointima formation. Nur77 mRNA is upregulated in cuffed arteries, with optimal expression after 6 hours and elevated expression up to 7 days after vascular injury. Local perivascular delivery of 6-MP with a drug-eluting cuff significantly inhibits neointima formation in wild-type mice. Locally applied 6-MP does not affect inflammatory responses or apoptosis but inhibits expression of proliferating cell nuclear antigen and enhances protein levels of the cell-cycle inhibitor p27(Kip1) in the vessel wall. An even stronger inhibition of neointima formation in response to local 6-MP delivery was observed in transgenic mice that overexpressed Nur77. In contrast, 6-MP does not alter lesion formation in transgenic mice that overexpress a dominant-negative variant of Nur77 in arterial SMCs, which provides evidence for the involvement of Nur77-like factors.


CONCLUSIONS
Enhancement of the activity of Nur77 by 6-MP protects against excessive SMC proliferation and SMC-rich neointima formation. We propose that activation of the nuclear receptor Nur77 is a rational approach to treating in-stent restenosis.
Pires
Nuno M M
NM
Gaubius Laboratory, TNO-Quality of Life, Leiden, The Netherlands.
Pols
Thijs W H
TW
de Vries
Margreet R
MR
van Tiel
Claudia M
CM
Bonta
Peter I
PI
Vos
Mariska
M
Arkenbout
E Karin
EK
Pannekoek
Hans
H
Jukema
J Wouter
JW
Quax
Paul H A
PH
de Vries
Carlie J M
CJ
D000818:Animals; D000964:Antimetabolites, Antineoplastic / Q000494:pharmacology*; D017209:Apoptosis / Q000187:drug effects; D002455:Cell Division / Q000187:drug effects; D002478:Cells, Cultured; D023903:Coronary Restenosis / Q000188:drug therapy* / Q000378:metabolism / Q000473:pathology; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D004195:Disease Models, Animal; D004343:Drug Implants; D005263:Femoral Artery / Q000473:pathology; D006801:Humans; D008297:Male; D015122:Mercaptopurine / Q000494:pharmacology*; D051379:Mice; D008815:Mice, Inbred Strains; D008822:Mice, Transgenic; D009131:Muscle, Smooth, Vascular / Q000187:drug effects* / Q000473:pathology; D057105:Nuclear Receptor Subfamily 4, Group A, Member 1; D012333:RNA, Messenger / Q000378:metabolism; D034741:RNA, Small Interfering; D018160:Receptors, Cytoplasmic and Nuclear / Q000235:genetics / Q000378:metabolism*; D011987:Receptors, Steroid / Q000235:genetics / Q000378:metabolism*; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism*; D017539:Tunica Intima / Q000187:drug effects / Q000473:pathology; D014469:Umbilical Arteries / Q000166:cytology
D000964:Antimetabolites, Antineoplastic; D004268:DNA-Binding Proteins; D004343:Drug Implants; C539821:NR4A1 protein, human; C539818:Nr4a1 protein, mouse; D057105:Nuclear Receptor Subfamily 4, Group A, Member 1; D012333:RNA, Messenger; D034741:RNA, Small Interfering; D018160:Receptors, Cytoplasmic and Nuclear; D011987:Receptors, Steroid; D014157:Transcription Factors; D015122:Mercaptopurine