Transcriptional up-regulation of nitric oxide synthase II by nuclear factor-κB at rostral ventrolateral medulla in a rat mevinphos intoxication model of brain stem death

Julie Y.H. Chan, Carol H.Y. Wu, Ching Yi Tsai, Hsiao Lei Cheng, Kuang Yu Dai, Samuel H.H. Chan, Alice Y.W. Chang

Research output: Contribution to journalArticlepeer-review

26 Citations (Scopus)

Abstract

As the origin of a 'life-and-death' signal that reflects central cardiovascular regulatory failure during brain stem death, the rostral ventrolateral medulla (RVLM) is a suitable neural substrate for mechanistic delineation of this vital phenomenon. Using a clinically relevant animal model that employed the organophosphate pesticide mevinphos (Mev) as the experimental insult, we evaluated the hypothesis that transcriptional up-regulation of nitric oxide synthase I or II (NOS I or II) gene expression by nuclear factor-κB (NF-κB) on activation of muscarinic receptors in the RVLM underlies brain stem death. In Sprague-Dawley rats maintained under propofol anaesthesia, co-microinjection of muscarinic M2R (methoctramine) or M4R (tropicamide), but not M1R (pirenzepine) or M3R (4-diphenylacetoxy-N-dimethylpiperidinium) antagonist significantly reduced the enhanced NOS I-protein kinase G signalling ('pro-life' phase) or augmented NOS II-peroxynitrite cascade ('pro-death' phase) in ventrolateral medulla, blunted the biphasic increase and decrease in baroreceptor reflex-mediated sympathetic vasomotor tone that reflect the transition from life to death, and diminished the elevated DNA binding activity or nucleus-bound translocation of NF-κB in RVLM neurons induced by microinjection of Mev into the bilateral RVLM. However, NF-κB inhibitors (diethyldithiocarbamate or pyrrolidine dithiocarbamate) or double-stranded κB decoy DNA preferentially antagonized the augmented NOS II-peroxynitrite cascade and the associated cardiovascular depression exhibited during the 'pro-death' phase. We conclude that transcriptional up-regulation of NOS II gene expression by activation of NF-κB on selective stimulation of muscarinic M2 or M4 subtype receptors in the RVLM underlies the elicited cardiovascular depression during the 'pro-death' phase in our Mev intoxication model of brain stem death.

Original languageEnglish
Pages (from-to)1293-1307
Number of pages15
JournalJournal of Physiology
Volume581
Issue number3
DOIs
Publication statusPublished - 2007 Jun 1

All Science Journal Classification (ASJC) codes

  • Physiology

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