一氧化氮與內皮素之間於新生鼠心臟細胞的交互作用

Abstract

Endothelin-1 (Et-1) treatment of cardiac myocytes (CM) induces cardiac hypertrophy. Cardiovascular release of nitric oxide (NO) may play a role during cardiac hypertrophy. The present study examined the protection mechanism of endogenously released NO on c-fos induction by Et-1 in neonatal rat CM. CM exposed to Et-1 induced NO release. Et-1 stimulated nitric oxide synthase (NOS) activity led to NO production that was attenuated by treating CM with an antagonist to endothelin B receptor. CM treated with a NO donor, S-nitroso-N-acetylpenicillamine (SNAP) or 3-morpholinosydnonimine (SIN-1), inhibited Et-1–induced c-fos expression. Conversely, CM treated with a NO scavenger, 2-phenyl-4,4,5,5,-tetramethyl-imidazoline-l-oxyl- 3-oxide (PTIO), augmented Et-1-induced c-fos expression. The attenuation of NO on c-fos expression was shown by reducing either c-fos mRNA levels or c-fos promoter activities using a chimera containing the c-fos promoter region (-2.25 kb) ligated to a reporter gene CAT. In contrast to the enhanced promoter activity in CM after PTIO treatment, attenuated Et-1-induced c-fos promoter activity was shown in CM treated with a NO donor. CM cotransfected with a dominant negative mutant of Ras (RasN17), Raf-1 (Raf301), or a catalytically inactive mutant of extracellular signal–regulated kinase (ERK)– 2 (mERK) inhibited Et-1–induced c-fos promoter activity, indicating Ras/Raf/ERK pathway was involved. NO modulation of this signaling pathway was shown by its inhibitory effect on Et-1–induced ERK activity. CM treated with NO resulted in a decrease of Et-1-induced binding of nuclear proteins to the AP-1 binding sequences. Furthermore, CM treated with a NO donor significantly suppressed Et-1-induced b-myosin heavy chain promoter activities. These results indicate that CM under Et-1 treatment increases NO levels and the increased NO attenuated Et-1-induced c-fos expression via the ERK signaling pathway. These findings support the importance of NO as a negative regulator in Et-1–induced gene expression and cardiac hypertrophy.