?-Adrenergic receptors stimulate interleukin-6 production through Epac-dependent activation of PKC?/p38 MAPK signalling in neonatal mouse cardiac fibroblasts.

ABSTRACT: BACKGROUND AND PURPOSE IL-6 plays crucial roles in cardiac hypertrophy, cardiac fibrosis and heart failure. Activation of ?-adrenoceptors induced IL-6 production in neonatal mouse cardiac fibroblasts (NMCFs) through a G(s) /adenylate cyclase/cAMP/p38 MAPK pathway but independent of PKA. However, how cAMP activates p38 MAPK is still not defined. In this study, we have assessed the role of the exchange protein directly activated by cAMP (Epac) and PKC? in p38 MAPK activation and IL-6 production by stimulated by the ?-adrenoceptor agonist isoprenaline in NMCFs. EXPERIMENTAL APPROACH The IL-6 concentration in cell culture supernatants was measured by ELISA. The levels of phosphorylated and total p38 MAPK and PKC? were determined by Western blot analysis. The translocation of PKC? was determined by immunoblotting the soluble and particulate fractions. Expression of Epac1 or PKC? was knocked down by the corresponding, adenovirus-mediated, small hairpin RNA (shRNA). RESULTS In NMCFs, activation of ?-adrenoceptors enhanced PKC? phosphorylation and translocation. Furthermore, knock-down of the PKC? isoform using an adenovirus-mediated shRNA markedly down-regulated IL-6 induction by NMCFs stimulated with isoprenaline. Moreover, knock-down of Epac1 confirmed that Epac1 was upstream of PKC? in IL-6 production. Additionally, both Epac1 and PKC? mediated the p38 MAPK activation induced by isoprenaline. CONCLUSIONS AND IMPLICATIONS ?-Adrenoceptor agonists activate a cAMP/Epac/PKC?/p38 MAPK pathway to produce IL-6 in NMCFs. This study identifies Epac as the link between cAMP and p38 MAPK signalling pathways and demonstrates that PKC? can function as a novel downstream effector of this ?-adrenoceptor/cAMP/Epac pathway.

SUBMITTER: Chen C 

PROVIDER: S-EPMC3417497 | biostudies-literature | 2012 May

REPOSITORIES: biostudies-literature