On the different roles of AT 1 and AT 2 receptors in stretch-induced changes of connexin43 expression and localisation
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SIGNALING AND CELL PHYSIOLOGY
On the different roles of AT1 and AT2 receptors in stretch-induced changes of connexin43 expression and localisation Aida Salameh & Daniel Apel & Jorge Gonzalez Casanova & Sandy von Salisch & Friedrich-Wilhelm Mohr & Ingo Daehnert & Stefan Dhein
Received: 25 May 2012 / Revised: 12 September 2012 / Accepted: 13 September 2012 # Springer-Verlag Berlin Heidelberg 2012
Abstract Cyclic mechanical stretch (CMS) and angiotensin II (ATII) play an important role in cardiac remodelling. Thus, we aimed to examine how ATII affects CMSinduced changes in localisation and expression of the gap junction protein connexin43 (Cx43). Neonatal rat cardiomyocytes cultured on gelatin-coated Flexcell cell culture plates were kept static or were exposed to CMS (110 % of resting length, 1 Hz) for 24 h with or without additional ATII (0.1 μmol/L). Moreover, inhibitors of ATII receptors (AT-R) were used (for AT1-R: losartan 0.1 μmol/L, for AT2R: PD123177 0.1 μmol/L). Thereafter, the cardiomyocytes were investigated by immunohistology, PCR and Western blot. After 24 h of CMS, cardiomyocytes were significantly elongated and orientated 75±1.6° nearly perpendicular to the stretch axis. Furthermore, CMS significantly accentuated Cx43 at the cell poles (ratio Cx43 polar/lateral static: 2.32±0.17; CMS: 10.08±3.2). Additional ATII application significantly reduced Cx43 polarisation (ratio Cx43 polar/ lateral ATII: 4.61±0.42). The combined administration of ATII and losartan to CMS further reduced Cx43 polarisation to control levels, whilst the AT2-R blocker PD123177 restored polarisation. Moreover, CMS and ATII application resulted in a significant Cx43 protein and Cx43 mRNA up-regulation which could be blocked by losartan but not by PD123177. Thus, CMS results in a self-organisation of the cardiomyocytes leading to elongated cells orientated transversely towards the stretch axis with enhanced Cx43 expression and Aida Salameh and Daniel Apel contributed equally to this study. A. Salameh (*) : J. Gonzalez Casanova : I. Daehnert Clinic for Paediatric Cardiology, University of Leipzig, Leipzig, Germany e-mail: [email protected] D. Apel : S. von Salisch : F.-W. Mohr : S. Dhein Clinic for Cardiac Surgery, University of Leipzig, Leipzig, Germany
Cx43 accentuation at the cell poles. ATII enhances total Cx43 mRNA and protein expression probably via AT 1 -R (0inhibitory effect of losartan) and reduces Cx43 polarisation presumably via AT2-R, since PD123177 (but not losartan) inhibited the negative effects of ATII on polarisation. Keywords Stretch . Angiotensin II . Cx43 . Angiotensin receptors Abbreviations ATII Angiotensin II AT1-R Angiotensin receptor type 1 AT2-R Angiotensin receptor type 2 Cx43 Connexin43 Ct Threshold cycle ERK1/2 Extracellular signal-regulated kinase 1/2 (0p42/44) FAK Focal adhesion kinase PCR Polymerase chain reaction ZO-1 Zonula occludens protein 1
Introduction Gap junction channels are essential for intercellular communication, and in the heart, they provide the basis for regular and dir
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