Protease-resistant insulin-like growth factor (IGF)-binding protein-4 inhibits IGF-I actions and neointimal expansion in a porcine model of neointimal hyperplasia.
IGF-I has been shown to play a role in the progression of atherosclerosis in experimental animal models. IGF-binding protein-4 (IGFBP-4) binds to IGF-I and prevents its association with receptors. Overexpression of a protease-resistant form of IGFBP-4 has been shown to inhibit the ability of IGF-I to stimulate normal smooth muscle cell growth in mice. Based on these observations, we prepared a protease-resistant form of IGFBP-4 and infused it into hypercholesterolemic pigs. Infusion of the protease-resistant mutant inhibited lesion development by 53.3 +/- 6.1% (n = 6; P < 0.01). Control vessels that received an equimolar concentration of IGF-I and the protease-resistant IGFBP-4 showed no reduction in lesion size compared with control lesions that were infused with vehicle. Infusion of a nonmutated form of IGFBP-4 did not significantly inhibit lesion development. Proliferating cell nuclear antigen analysis showed that the mutant IGFBP-4 appeared to inhibit cell proliferation. The area occupied by extracellular matrix was also reduced proportionally compared with total lesion area. Immunoblotting revealed that the mutant IGFBP-4 remained intact, whereas the wild-type IGFBP-4 that was infused was proteolytically cleaved. Further analysis of the lesions revealed that a marker protein, IGFBP-5, whose synthesis is stimulated by IGF-I, was decreased in the lesions that received the protease-resistant, IGFBP-4 mutant, whereas there was no change in lesions that received wild-type IGFBP-4 or the mutant protein plus IGF-I. These findings clearly illustrate that infusion of protease-resistant IGFBP-4 into the perilesion environment results in inhibition of cell proliferation and attenuation of the development of neointima. The findings support the hypothesis that inhibiting IGFBP-4 proteolysis in the lesion microenvironment could be an effective means for regulating neointimal expansion.
Nichols
T C
TC
Division of Endocrinology, University of North Carolina at Chapel Hill, 8024 Burnett-Womack, Chapel Hill, NC 27599-7170, USA.
Busby
W H
WH
Merricks
E
E
Sipos
J
J
Rowland
M
M
Sitko
K
K
Clemmons
D R
DR
D000818:Animals; D002339:Carotid Arteries / Q000187:drug effects / Q000378:metabolism / Q000473:pathology; D049109:Cell Proliferation / Q000187:drug effects; D004351:Drug Resistance; D005260:Female; D005263:Femoral Artery / Q000187:drug effects / Q000378:metabolism / Q000473:pathology; D006937:Hypercholesterolemia / Q000378:metabolism / Q000473:pathology*; D006965:Hyperplasia; D018974:Insulin-Like Growth Factor Binding Protein 4 / Q000737:chemistry* / Q000235:genetics / Q000494:pharmacology*; D018975:Insulin-Like Growth Factor Binding Protein 5 / Q000037:antagonists & inhibitors; D007334:Insulin-Like Growth Factor I / Q000037:antagonists & inhibitors* / Q000378:metabolism / Q000494:pharmacology; D008297:Male; D009154:Mutation; D010447:Peptide Hydrolases / Q000378:metabolism*; D013552:Swine; D014162:Transfection; D017539:Tunica Intima / Q000187:drug effects / Q000378:metabolism / Q000473:pathology*
D018974:Insulin-Like Growth Factor Binding Protein 4; D018975:Insulin-Like Growth Factor Binding Protein 5; D007334:Insulin-Like Growth Factor I; D010447:Peptide Hydrolases