Modulation of clusterin isoforms is associated with all-trans retinoic acid-induced proliferative arrest and apoptosis of intimal smooth muscle cells.
OBJECTIVE
Clusterin is a heterodimeric glycoprotein which is implicated in several biological processes. The nuclear (n-CLU) and cytoplasmic secreted (s-CLU) isoforms have recently been described, but their role is still unclear. The aim of this study is to investigate the expression of clusterin and its isoforms during proliferative arrest and apoptosis of vascular smooth muscle cells (SMCs).


RESULTS
Clusterin expression was evaluated by immunohistochemistry and Western blotting in human arteries and rat aortas. In human diffuse myointimal thickening, clusterin was detected in cell cytoplasm and extracellular space, whereas it was practically absent in the media. In rat aortas 15 days after ballooning, intimal cells (IT cells) overexpressed s-CLU and n-CLU, the latter mainly in the inner neointima; clusterin expression decreased at 60 days. In vitro, IT cells maintained high clusterin expression and its antisense markedly reduced proliferation and increased apoptosis. Western blotting showed that all-trans retinoic acid-induced proliferative arrest and increased alpha-smooth muscle actin expression did associate to s-CLU and B-myb reduction, whereas bax-related apoptosis was associated to a shift from the s-CLU to n-CLU isoform.


CONCLUSIONS
Clusterin overexpression characterized neointimal SMCs; s-CLU expression decreased in IT cells during all-trans retinoic acid-induced proliferative arrest and redifferentiation, whereas n-CLU overexpression was characteristic of apoptosis. Clusterin was detected in human arterial myointimal thickening and absent in the underlying media. Rat neointimal cells overexpressed clusterin and clusterin antisense oligonucleotide reduced proliferation and increased apoptosis. All-trans retinoic acid-induced proliferative arrest showed association with s-CLU reduction and n-CLU overexpression with apoptosis, supporting a different biological role of these isoforms.
Orlandi
Augusto
A
Anatomic Pathology Institute, Department of Biopathology and Image Diagnostics, Tor Vergata University of Rome, Via Montpellier 1, 00133 Rome, Italy. orlandi@uniroma2.it
Pucci
Sabina
S
Ciucci
Alessandro
A
Pichiorri
Flavia
F
Ferlosio
Amedeo
A
Spagnoli
Luigi Giusto
LG
D000818:Animals; D001011:Aorta; D001013:Aorta, Thoracic / Q000293:injuries / Q000473:pathology; D017209:Apoptosis / Q000187:drug effects*; D002404:Catheterization / Q000009:adverse effects; D018797:Cell Cycle Proteins / Q000096:biosynthesis / Q000235:genetics; D002455:Cell Division / Q000187:drug effects; D002467:Cell Nucleus / Q000378:metabolism; D002478:Cells, Cultured / Q000166:cytology / Q000187:drug effects / Q000378:metabolism; D051152:Clusterin; D004268:DNA-Binding Proteins / Q000096:biosynthesis / Q000235:genetics; D005260:Female; D005786:Gene Expression Regulation / Q000187:drug effects*; D006023:Glycoproteins / Q000096:biosynthesis* / Q000235:genetics; D006801:Humans; D007473:Ion Channels / Q000096:biosynthesis* / Q000235:genetics; D008565:Membrane Proteins / Q000096:biosynthesis* / Q000235:genetics; D008638:Mesenteric Arteries / Q000166:cytology; D018832:Molecular Chaperones / Q000096:biosynthesis* / Q000235:genetics; D009131:Muscle, Smooth, Vascular / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism; D032389:Myocytes, Smooth Muscle / Q000187:drug effects* / Q000378:metabolism; D020319:Oligodeoxyribonucleotides, Antisense / Q000494:pharmacology; D020033:Protein Isoforms / Q000096:biosynthesis / Q000235:genetics; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000378:metabolism; D051381:Rats; D017208:Rats, Wistar; D050053:TRPM Cation Channels; D015534:Trans-Activators / Q000096:biosynthesis / Q000235:genetics; D014157:Transcription Factors / Q000096:biosynthesis / Q000235:genetics; D014212:Tretinoin / Q000494:pharmacology*; D017539:Tunica Intima / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism; D014599:Uterus / Q000098:blood supply; D051028:bcl-2-Associated X Protein
C494826:BAX protein, human; C494828:Bax protein, rat; C495242:CLU protein, human; D018797:Cell Cycle Proteins; D051152:Clusterin; D004268:DNA-Binding Proteins; D006023:Glycoproteins; D007473:Ion Channels; C064352:MYBL2 protein, human; D008565:Membrane Proteins; D018832:Molecular Chaperones; C498883:Mybl2 protein, rat; D020319:Oligodeoxyribonucleotides, Antisense; D020033:Protein Isoforms; D019253:Proto-Oncogene Proteins c-bcl-2; D050053:TRPM Cation Channels; C121934:TRPM2 protein, human; D015534:Trans-Activators; D014157:Transcription Factors; D051028:bcl-2-Associated X Protein; D014212:Tretinoin