Up-regulation of endothelin type B receptors in the human internal mammary artery in culture is dependent on protein kinase C and mitogen-activated kinase signaling pathways

BACKGROUND: Up-regulation of vascular endothelin type B (ET(B)) receptors is implicated in the pathogenesis of cardiovascular disease. Culture of intact arteries has been shown to induce similar receptor alterations and has therefore been suggested as a suitable method for, ex vivo, in detail delineation of the regulation of endothelin receptors. We hypothesize that mitogen-activated kinases (MAPK) and protein kinase C (PKC) are involved in the regulation of endothelin ET(B )receptors in human internal mammary arteries. METHODS: Human internal mammary arteries were obtained during coronary artery bypass graft surgery and were studied before and after 24 hours of organ culture, using in vitro pharmacology, real time PCR and Western blot techniques. Sarafotoxin 6c and endothelin-1 were used to examine the endothelin ET(A )and ET(B )receptor effects, respectively. The involvement of PKC and MAPK in the endothelin receptor regulation was examined by culture in the presence of antagonists. RESULTS: The endohtelin-1-induced contraction (after endothelin ET(B )receptor desensitization) and the endothelin ET(A )receptor mRNA expression levels were not altered by culture. The sarafotoxin 6c contraction, endothelin ET(B )receptor protein and mRNA expression levels were increased after organ culture. This increase was antagonized by; (1) PKC inhibitors (10 μM bisindolylmaleimide I and 10 μM Ro-32-0432), and (2) inhibitors of the p38, extracellular signal related kinases 1 and 2 (ERK1/2) and C-jun terminal kinase (JNK) MAPK pathways (10 μM SB203580, 10 μM PD98059 and 10 μM SP600125, respectively). CONCLUSION: In conclusion, PKC and MAPK seem to be involved in the up-regulation of endothelin ET(B )receptor expression in human internal mammary arteries. Inhibiting these intracellular signal transduction pathways may provide a future therapeutic target for hindering the development of vascular endothelin ET(B )receptor changes in cardiovascular disease.