Protein kinase A-dependent Neuronal Nitric Oxide Synthase Activation Mediates the Enhancement of Baroreflex Response by Adrenomedullin in the Nucleus Tractus Solitarii of Rats

Journal of Biomedical Science

Research

Ya-Jou Lou¹  I-Chin Chen¹  Lih-Chi Chen¹  Jiin-Cherng Yen²  David HT Yen³  I-Chun Ho⁴  Ying-Chen Chiu⁴  Yuh-Chiang Shen⁵ 

[1] Department of Pharmacy, Taipei City Hospital, Taipei, Taiwan;Department of Pharmacy, Taipei City Hospital, Taipei, Taiwan;Institute of Pharmacology, School of Medicine, National Yang-Ming University, Taipei, Taiwan;Institute of Emergency and Critical Care Medicine, School of Medicine, National Yang-Ming University, Taipei, Taiwan;Emergency Department, Taipei Veterans General Hospital, Taipei, Taiwan;Institute of Pharmacology, School of Medicine, National Yang-Ming University, Taipei, Taiwan;National Research Institute of Chinese Medicine, Taipei, Taiwan;

关键词: Nitric Oxide;    Test Agent;    Nucleus Tractus Solitarii;    nNOS Activation;    Nucleus Tractus Solitarii Neuron;   

DOI  :  10.1186/1423-0127-18-32

 received in 2011-03-24, accepted in 2011-05-19,  发布年份 2011

来源: Springer

【 摘 要 】

BackgroundAdrenomedullin (ADM) exerts its biological functions through the receptor-mediated 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).MethodsIntravenous 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.ResultsWe 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.ConclusionsThe 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.

【 授权许可】

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© Yen et al; licensee BioMed Central Ltd. 2011