title: Autocrine regulation of myocyte Cx43 expression by VEGF.
abstract: Cardiac myocytes can rapidly adjust their expression of gap junction channel proteins in response to changes in load. Previously, we showed that after only 1 hour of linear pulsatile stretch (110% of resting cell length; 3 Hz), expression of connexin43 (Cx43) by cultured neonatal rat ventricular myocytes is increased by approximately 2-fold and impulse propagation is significantly more rapid. In the present study, we tested the hypothesis that vascular endothelial growth factor (VEGF), acting downstream of transforming growth factor-beta (TGF-beta), mediates stretch-induced upregulation of Cx43 expression by cardiac myocytes. Incubation of nonstretched cells with exogenous VEGF (100 ng/mL) or TGF-beta (10 ng/mL) for 1 hour increased Cx43 expression by approximately 1.8-fold, comparable to that observed in cells subjected to pulsatile stretch for 1 hour. Stretch-induced upregulation of Cx43 expression was blocked by either anti-VEGF antibody or anti-TGF-beta antibody. Stretch-induced enhancement of conduction was also blocked by anti-VEGF antibody. ELISA assay showed that VEGF was secreted into the culture medium during stretch. Furthermore, stretch-conditioned medium stimulated Cx43 expression in nonstretched cells. This effect was also blocked by anti-VEGF antibody. Upregulation of Cx43 expression stimulated by exogenous TGF-beta was blocked by anti-VEGF antibody, but VEGF-stimulation of Cx43 expression was not blocked by anti-TGF-beta antibody. Thus, stretch-induced upregulation of Cx43 expression is mediated, at least in part, by VEGF, which acts downstream of TGF-beta. Because the cultures contained only approximately 5% nonmyocytic cells, these results indicate that myocyte-derived VEGF, secreted in response to stretch, acts in an autocrine fashion to enhance intercellular coupling.
authors.affiliation: Department of Medicine, Washington University School of Medicine, St Louis, MO, USA.
authors.forename: Rhea C
authors.initials: RC
authors.lastname: Pimentel
authors.forename: Kathryn A
authors.initials: KA
authors.lastname: Yamada
authors.forename: André G
authors.initials: AG
authors.lastname: Kléber
authors.forename: Jeffrey E
authors.initials: JE
authors.lastname: Saffitz
mesh_terms: D000818:Animals; D019898:Autocrine Communication / Q000502:physiology; D002478:Cells, Cultured; D018031:Connexin 43 / Q000235:genetics / Q000502:physiology*; D016228:Endothelial Growth Factors / Q000378:metabolism / Q000494:pharmacology / Q000502:physiology*; D006321:Heart / Q000502:physiology*; D008222:Lymphokines / Q000378:metabolism / Q000494:pharmacology / Q000502:physiology*; D009200:Myocardial Contraction / Q000502:physiology*; D051381:Rats; D011921:Rats, Inbred WKY; D016212:Transforming Growth Factor beta / Q000494:pharmacology; D015854:Up-Regulation / Q000187:drug effects / Q000502:physiology*; D042461:Vascular Endothelial Growth Factor A; D042442:Vascular Endothelial Growth Factors
chemical_list: D018031:Connexin 43; D016228:Endothelial Growth Factors; D008222:Lymphokines; D016212:Transforming Growth Factor beta; D042461:Vascular Endothelial Growth Factor A; D042442:Vascular Endothelial Growth Factors