An-Najah Staff

ABSTRACT Cardiac fibroblasts (CF) play a major role in fibrogenesis associated with heart failure as they are responsible for the production of ECM components as well as the secretion of several important fibrosis-associated mediators, such as connective tissue growth factor (CTGF). Here we investigate the role of Ca2+-dependent signaling pathway in the regulation of CTGF expression and secretion, which is induced by Angiotensin II (Ang II) type1 receptor (AT1-R) in neonatal rat CF. Ca2+ transient in response to Ang II was inhibited upon AT1-R blockade and phospholipase-C-β (PLC- β) inhibition by valsartan and U73122 respectively. Ang II was still able to induce Ca2+ transient even in the absence of Ca2+ in culture medium, moreover the depletion or chelation of intracellular Ca2+ by thapsigargin and BAPTA-AM respectively inhibited Ca2+ transient. At the protein level, treatment with BAPTA-AM was associated with an inhibition of Ang II effect on intracellular CTGF content as well as on CTGF secretion, but there was no effect on the basal protein levels of CTGF. At the mRNA level, BAPTA-AM inhibited both the basal and Ang II-induced CTGF mRNA transcription. The blockade of IP3 receptors by xestospongin-C inhibited Ang II-induced Ca2+ transient, which was associated with an inhibition of basal and Ang II-induced CTGF secretion, but there was no effect on intracellular CTGF content. In contrast, the blockade of TRPC3 Ca2+ channels on cell membrane by Pyr3 enhanced Ang II-induced Ca2+ transient, which was associated with an increase in CTGF secretion. However, there was no effect on the level of mRNA CTGF transcription. The inhibition of calcineurin by cyclosporine-A had no effect on Ang II-induced Ca2+ transient, however it induced CTGF mRNA transcription, while intracellular CTGF content was reduced. In conclusion, Ang II induces Ca2+ transient via PLC- β dependent pathway, which is generated mainly from intracellular Ca2+ stores. The contribution of extracellular Ca2+ is minor and seems to tune the release of intracellular Ca2+. Ca2+ coming from different sources contribute differently to the regulation of CTGF expression and secretion.

Calcium complexly regulate connective tissue growth factor in cardiac fibroblasts. Available from: https://www.researchgate.net/publication/269706610_Calcium_complexly_regulate_connective_tissue_growth_factor_in_cardiac_fibroblasts [accessed Apr 29, 2015].