- 作者: David H.T. Yen; Lih-Chi Chen; Yuh-Chiang Shen; Ying-Chen Chiu; I-Chun Ho; Ya-Jou Lou; I-Chin Chen; Jiin-Cherng Yen
- 作者服務機構: Institute of Emergency and Critical Care Medicine, School of Medicine, National Yang-Ming University, Taipei, Taiwan, R.O.C.
- 中文摘要: --
- 英文摘要:
Background: Adrenomedullin (ADM) exerts its biological functions through the receptormediated
enzymatic mechanisms that involve protein kinase A (PKA), or
neuronal nitric oxide synthase (nNOS). We previously demonstrated that the
receptor-mediated cAMP/PKA pathway involves in ADM-enhanced
baroreceptor reflex (BRR) response. It remains unclear whether ADM may
enhance BRR response via activation of nNOS-dependent mechanism in the
nucleus tractus solitarii (NTS).
Methods: Intravenous injection of phenylephrine was administered to evoke the BRR
before and at 10, 30, and 60 min after microinjection of the test agents into
NTS of Sprague-Dawley rats. Western blotting analysis was used to measure
the level and phosphorylation of proteins that involved in BRR-enhancing
effects of ADM (0.2 pmol) in NTS. The colocalization of PKA and nNOS was
examined by immunohistochemical staining and observed with a laser
confocal microscope.
Results: We found that ADM-induced enhancement of BRR response was blunted by
microinjection of NPLA or Rp-8-Br-cGMP, a selective inhibitor of nNOS or
protein kinase G (PKG) respectively, into NTS. Western blot analysis further
revealed that ADM induced an increase in the protein level of PKG-I which
could be attenuated by co-microinjection with the ADM receptor antagonist
ADM22-52 or NPLA. Moreover, we observed an increase in phosphorylation at
Ser1416 of nNOS at 10, 30, and 60 min after intra-NTS administration of
ADM. As such, nNOS/PKG signaling may also account for the enhancing
effect of ADM on BRR response. Interestingly, biochemical evidence further
showed that ADM-induced increase of nNOS phosphorylation was prevented
by co-microinjection with Rp-8-Br-cAMP, a PKA inhibitor. The possibility of
PKA-dependent nNOS activation was substantiated by immunohistochemical
demonstration of co-localization of PKA and nNOS in putative NTS neurons.
Conclusions: The novel finding of this study is that the signal transduction cascade that
underlies the enhancement of BRR response by ADM in NTS is composed
sequentially of cAMP/PKA and nNOS/PKG pathways. - 中文關鍵字: --
- 英文關鍵字: --