Autocrine regulation of myocyte Cx43 expression by VEGF.
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.
Pimentel
Rhea C
RC
Department of Medicine, Washington University School of Medicine, St Louis, MO, USA.
Yamada
Kathryn A
KA
Kléber
André G
AG
Saffitz
Jeffrey E
JE
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
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