Potential Role of Brain Stem Extra-endothelial Activity of eNOS for the Regulation of Blood Pressure

In the cardiovascular system NO is continuously produced by the type III isoform of nitric oxide synthase (eNOS), which is not only expressed in vascular endothelial cells, but also in many other cell types of the body such as astrocytes, blood cells and nephron epithelial cells. Disruption of eNOS in mice (eNOS-KO) causes a profound increase of blood pressure which is frequently assumed to be caused by the lack of endothelium-derived nitric oxide generation. By crossing a transgenic mouse model with endothelial specific overexpression of eNOS on C57Bl/6 background (eNOS-Tg) with eNOS-KO, a double transgenic mouse line expressing eNOS exclusively in the vascular endothelium has been generated (eNOS-Tg/eNOS-KO). This endothelium-specific reintroduction of eNOS in eNOS-KO, i.e. vascular-specific eNOS rescue, resulted in restoration of endothelial eNOS activity in conductance and resistance arteries but did not lower blood pressure suggesting that the eNOS-mediated local vasodilator activity alone can not compensate for the lack of non-vascular eNOS-dependent components in the regulation of blood pressure. The current research project aims to investigate the contribution of extra-endothelial brain stem eNOS activity for the physiologic regulation of blood pressure. To accomplish this, microinjections of the lentiviral particles encoding eNOS or inhibitory eNOS short hairpin RNA will be performed into the nucleus of the solitary tract (NTS) and into the rostral ventrolateral medulla (RVLM) of eNOS-Tg/eNOS-KO, eNOS-KO and C57Bl/6 mice. Transduction of the gene will be evaluated with regards to localization, cell type specifity and stability over time and the effects of lentiviral brain stem driven eNOS re-expression or short hairpin RNA induced eNOS knock-down on blood pressure and heart rate will be investigated. These studies will be complemented by measurements of brain stem eNOS mRNA, protein expression and activity and by evaluation of sympathetic outflow and catecholamine excretion. The newly established transgenic mouse model eNOS-Tg/eNOS-KO represents a unique in-vivo tool and is expected to provide valuable new insights into the role of non-endothelial eNOS-activity for the physiological blood pressure regulation.

DFG Programme Research Grants

Participating Institution Goethe-Universität Frankfurt am Main
Universitätsklinikum
Institut für Klinische Pharmakologie

Participating Person Professor Georg Kojda, Ph.D.