title: Inhibitory effects of tranilast on expression of transforming growth factor-beta isoforms and receptors in injured arteries.
abstract: Tranilast (N(3,4-dimethoxycinnamoyl)anthranilic acid), an agent which in cell culture inhibits transforming growth factor-beta (TGF-beta) secretion and antagonises the effects of TGF-beta and platelet-derived growth factor (PDGF) on cell migration and proliferation, has been reported to reduce the incidence of restenosis after angioplasty in angiographically validated human clinical trials. We investigated in a rat model of balloon angioplasty whether tranilast's effects in vivo could be attributed to inhibition of expression of TGF-beta and/or its receptor types. Using a standardised reverse transcriptase-polymerase chain reaction (RT-PCR) assay, we examined the effects of three doses of tranilast (25, 50 and 100 mg/kg) on the expression of two TGF-beta isoforms, the types I and II TGF-beta receptors and two putative TGF-beta responses, induction of integrins alpha(v) and beta3 mRNA, 2 h after oral administration and 26 h after vessel injury. Tranilast attenuated in a dose-dependent and reversible manner the injury-induced increases in mRNA levels encoding TGF-beta1, TGF-beta3, two type I TGF-beta receptors ALK-5 and ALK-2, and the type II receptor TbetaRII. At the highest dose mRNA levels encoding TGF-beta1 and TbetaRII were attenuated to levels approaching or below those observed in uninjured vessels. Messenger RNAs encoding TGF-beta3, ALK-5 and ALK-2 were all attenuated by between 70 and 74% (all P < 0.05). Tranilast also attenuated in a reversible manner the elevations in mRNA levels for integrins alpha(v) and beta3 observed after vessel injury, by 90 and 72%, respectively. We also investigated, in cultured smooth muscle cells derived from injured carotid arteries, the extent to which tranilast (300 mg/l) attenuated any increases in expression of type I and type II receptors stimulated by PDGF-BB and TGF-beta1, growth factors implicated in smooth muscle cell migration and proliferation in injured vessels. Increases in mRNA levels of the type I receptors ALK-5 and ALK-2 induced by PDGF-BB and TGF-beta1 were almost completely prevented by tranilast. Tranilast also prevented the PDGF-BB induced increases in TbetaRII but only partially inhibited the TGF-beta1 induced upregulation of TbetaRII. We conclude that tranilast can inhibit transcriptional mechanisms associated with the upregulation of TGF-beta and its receptor types in balloon catheter injured vessels. It is possible that these mechanisms contribute to its ability to reduce the frequency of restenosis after angioplasty.
authors.affiliation: Cell Biology Laboratory, Baker Medical Research Institute, Prahran, VIC, Australia. mward@baker.edu.au
authors.forename: M R
authors.initials: MR
authors.lastname: Ward
authors.forename: T
authors.initials: T
authors.lastname: Sasahara
authors.forename: A
authors.initials: A
authors.lastname: Agrotis
authors.forename: R J
authors.initials: RJ
authors.lastname: Dilley
authors.forename: G L
authors.initials: GL
authors.lastname: Jennings
authors.forename: A
authors.initials: A
authors.lastname: Bobik
mesh_terms: D000800:Angioplasty, Balloon / Q000009:adverse effects; D000818:Animals; D001157:Arterial Occlusive Diseases / Q000209:etiology / Q000378:metabolism*; D002339:Carotid Arteries / Q000187:drug effects* / Q000473:pathology; D020212:Carotid Artery Injuries; D002455:Cell Division / Q000187:drug effects; D002465:Cell Movement / Q000187:drug effects; D002478:Cells, Cultured; D017931:DNA Primers / Q000737:chemistry; D004305:Dose-Response Relationship, Drug; D016023:Integrins / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism; D008297:Male; D009131:Muscle, Smooth, Vascular / Q000378:metabolism / Q000473:pathology; D010975:Platelet Aggregation Inhibitors / Q000494:pharmacology*; D016133:Polymerase Chain Reaction; D012333:RNA, Messenger / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D018125:Receptors, Transforming Growth Factor beta / Q000037:antagonists & inhibitors* / Q000235:genetics / Q000378:metabolism; D016212:Transforming Growth Factor beta / Q000037:antagonists & inhibitors* / Q000235:genetics / Q000378:metabolism; D062367:ortho-Aminobenzoates / Q000494:pharmacology*
chemical_list: D017931:DNA Primers; D016023:Integrins; D010975:Platelet Aggregation Inhibitors; D012333:RNA, Messenger; D018125:Receptors, Transforming Growth Factor beta; D016212:Transforming Growth Factor beta; D062367:ortho-Aminobenzoates; C012293:tranilast