Up-regulation of connexin43 correlates with increased synthetic activity and enhanced contractile differentiation in TGF-beta-treated human aortic smooth muscle cells.
Up-regulation of the gap-junctional protein connexin43 (Cx43) in arterial smooth muscle cells (SMCs) features in response to injury and in atherosclerosis, in parallel with phenotypic transition to the synthetic state. TGF-beta1 is known to have a role in SMC differentiation and extracellular matrix (ECM) synthesis, key characteristics of phenotypic state. Here, we set out to examine the effects of TGF-beta1 on Cx43-gap junction expression in relation to SMC differentiation, ECM synthesis and growth. Cx43 expression was analysed by immunoconfocal microscopy and Western blotting in primary human aortic SMCs treated with TGF-beta1 over a 48-h period, with assessment of gap-junctional communication by cell-to-cell transfer of microinjected ethidium bromide. In parallel, synthetic activity was analysed by Northern blotting for ECM components alpha-1(I) and alpha1(III) procollagen transcripts, contractile differentiation was assessed by immunoconfocal microscopy and Western blotting of the markers smooth muscle alpha-actin, calponin and smooth muscle heavy chain isoform 1 (SM1), and growth was measured by BrdU incorporation. Our results demonstrate that TGF-beta1 significantly up-regulates Cx43 expression and intercellular communication, in concert with increased expression of alpha-actin, calponin and SM1. Concomitant with contractile protein expression, ECM synthesis was increased rather than decreased, TGF-beta1 inducing a significant up-regulation of both procollagen transcripts. These effects were independent of growth. We conclude that in human aortic SMCs, TGF-beta1 treatment leads to up-regulation of Cx43-mediated gap-junctional communication and increased synthetic activity yet, somewhat paradoxically, also enhanced contractile differentiation.
Rama
Aisha
A
Cardiac Medicine, National Heart and Lung Institute (Imperial College), Guy Scadding Building, Dovehouse Street, London SW3 6LY, UK.
Matsushita
Tsutomu
T
Charolidi
Nicoletta
N
Rothery
Stephen
S
Dupont
Emmanuel
E
Severs
Nicholas J
NJ
D000199:Actins / Q000378:metabolism; D001011:Aorta / Q000033:anatomy & histology*; D002450:Cell Communication / Q000502:physiology; D002454:Cell Differentiation / Q000502:physiology; D049109:Cell Proliferation; D048430:Cell Shape; D002478:Cells, Cultured; D018031:Connexin 43 / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D009119:Muscle Contraction / Q000502:physiology*; D009131:Muscle, Smooth, Vascular / Q000166:cytology*; D032389:Myocytes, Smooth Muscle / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism; D011347:Procollagen / Q000378:metabolism; D053773:Transforming Growth Factor beta1 / Q000494:pharmacology*; D015854:Up-Regulation
D000199:Actins; D018031:Connexin 43; C500216:GJA1 protein, human; D011347:Procollagen; D053773:Transforming Growth Factor beta1