Synergistic effects of growth factors on the regulation of smooth muscle cell scavenger receptor activity.
Rabbit smooth muscle cells (SMC) express types I and II scavenger receptors (ScR) that are up-regulated by platelet secretion products. In the current studies we investigated the effect of growth factors secreted by platelets on ScR activity in rabbit and human SMC. Platelet-derived growth factor (PDGF BB) and transforming growth factor beta 1 (TGF-beta 1) at 10 ng/ml increased ScR activity in rabbit SMC (by approximately 4- and 2-fold, respectively) but not in human SMC. Epidermal growth factor (EGF) or insulin-like growth factor I (IGF-I) alone had little effect on SMC ScR activity. The growth factors had synergistic effects on ScR activity and on types I and II ScR mRNA expression. In rabbit SMC, PDGF BB, EGF, and TGF-beta 1 together stimulated ScR activity 12-fold. In human SMC, EGF and TGF-beta 1, together with either IGF-I or PDGF BB, stimulated receptor activity approximately 7-fold. Growth factor-mediated induction of ScR activity in rabbit and human SMC was blocked by the tyrosine kinase inhibitor tyrphostin 47, whereas the induction of ScR activity in rabbit but not human SMC was blocked by the protein kinase C inhibitor MDL.29,152. Studies using neutralizing antibodies demonstrated that TGF-beta 1 is the predominant factor in in vitro preparations of platelet secretory products which regulates ScR activity. The growth factors that act synergistically in regulating ScR activity in vitro are all present in atherosclerotic lesions, where they are produced by macrophages, endothelial cells, SMC, and platelets. The data suggest that these growth factors may regulate ScR activity in SMC in vivo and contribute to foam cell formation.
Gong
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Gladstone Institute of Cardiovascular Disease, University of California, San Francisco 94141-9100, USA.
Pitas
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D000818:Animals; D000077214:Becaplermin; D001792:Blood Platelets / Q000502:physiology*; D002460:Cell Line; D004357:Drug Synergism; D004815:Epidermal Growth Factor / Q000494:pharmacology; D015870:Gene Expression / Q000187:drug effects; D006133:Growth Substances / Q000494:pharmacology*; D006801:Humans; D007334:Insulin-Like Growth Factor I / Q000494:pharmacology; D007700:Kinetics; D008077:Lipoproteins, LDL / Q000378:metabolism*; D008565:Membrane Proteins; D009130:Muscle, Smooth / Q000187:drug effects / Q000378:metabolism*; D009570:Nitriles / Q000494:pharmacology; D010081:Oxazolone / Q000031:analogs & derivatives / Q000494:pharmacology; D010636:Phenols / Q000494:pharmacology; D010982:Platelet-Derived Growth Factor / Q000494:pharmacology; D011493:Protein Kinase C / Q000037:antagonists & inhibitors; D011505:Protein-Tyrosine Kinases / Q000037:antagonists & inhibitors; D020574:Proto-Oncogene Proteins c-sis; D011804:Quinolines / Q000494:pharmacology; D011817:Rabbits; D011971:Receptors, Immunologic / Q000096:biosynthesis / Q000187:drug effects* / Q000378:metabolism; D018110:Receptors, Lipoprotein; D051116:Receptors, Scavenger; D011994:Recombinant Proteins / Q000494:pharmacology; D051122:Scavenger Receptors, Class B; D013045:Species Specificity; D016212:Transforming Growth Factor beta / Q000494:pharmacology; D020032:Tyrphostins
D006133:Growth Substances; D008077:Lipoproteins, LDL; D008565:Membrane Proteins; D009570:Nitriles; D010636:Phenols; D010982:Platelet-Derived Growth Factor; D020574:Proto-Oncogene Proteins c-sis; D011804:Quinolines; D011971:Receptors, Immunologic; D018110:Receptors, Lipoprotein; D051116:Receptors, Scavenger; D011994:Recombinant Proteins; C454739:Scarb1 protein, mouse; D051122:Scavenger Receptors, Class B; D016212:Transforming Growth Factor beta; D020032:Tyrphostins; C060152:tyrphostin 47; C073398:MDL 29152; D010081:Oxazolone; D000077214:Becaplermin; D004815:Epidermal Growth Factor; D007334:Insulin-Like Growth Factor I; D011505:Protein-Tyrosine Kinases; D011493:Protein Kinase C