Elevated Blood Pressure in Transgenic Mice With Brain-Specific Expression of Human Angiotensinogen Driven by the Glial Fibrillary Acidic Protein Promoter

• Published in: Circulation research Vol. 89; no. 4; pp. 365 - 372
• Main Authors: Morimoto, Satoshi, Cassell, Martin D, Beltz, Terry G, Johnson, Alan Kim, Davisson, Robin L, Sigmund, Curt D
• Format: Journal Article
• Language: English
• Published: Hagerstown, MD American Heart Association, Inc 17.08.2001; Lippincott; Lippincott Williams & Wilkins Ovid Technologies
• Subjects: Angiotensinogen - biosynthesis; Angiotensinogen - blood; Angiotensinogen - genetics; Animals; Arterial hypertension. Arterial hypotension; Astrocytes - metabolism; Biological and medical sciences; Blood and lymphatic vessels; Blood Pressure - drug effects; Blood Pressure - genetics; Brain - metabolism; Cardiology. Vascular system; Clinical manifestations. Epidemiology. Investigative techniques. Etiology; Dose-Response Relationship, Drug; Drinking - drug effects; Drinking - genetics; Gene Expression; Glial Fibrillary Acidic Protein - genetics; Humans; Hypertension - genetics; Hypertension - physiopathology; Injections, Intravenous; Injections, Intraventricular; Losartan - administration & dosage; Medical sciences; Mice; Mice, Transgenic; Neurons - metabolism; Organ Specificity - genetics; Promoter Regions, Genetic; Renin - administration & dosage; Renin - antagonists & inhibitors; Renin - genetics; RNA, Messenger - biosynthesis; Subfornical Organ - metabolism; Transgenes; Water-Electrolyte Balance - genetics; Hypertension; Animal model; Transcription promoter; Neuroglia; Glial fibrillary acidic protein; Rodentia; Central nervous system; Transgenic animal; Tissue specificity; Cardiovascular disease; Astrocyte; Gene expression; Prohormone; Renin angiotensin system; Vertebrata; Mammalia; Mouse; Angiotensinogen; Blood pressure; Hemodynamics; Brain (vertebrata)
• ISSN: 0009-7330; 1524-4571
• DOI: 10.1161/hh1601.094988

In addition to the circulatory renin (REN)–angiotensin system (RAS), a tissue RAS having an important role in cardiovascular function also exists in the central nervous system. In the brain, angiotensinogen (AGT) is expressed in astrocytes and in some neurons important to cardiovascular control, but its functional role remains undefined. We generated a transgenic mouse encoding the human AGT (hAGT) gene under the control of the human glial fibrillary acidic protein (GFAP) promoter to experimentally dissect the role of brain versus systemically derived AGT. This promoter targets expression of transgene products to astrocytes, the most abundant cell type expressing AGT in brain. All transgenic lines exhibited hAGT mRNA expression in brain, with variable expression in other tissues. In one line examined in detail, transgene expression was high in brain and low in tissues outside the central nervous system, and the level of plasma hAGT was not elevated over baseline. In the brain, hAGT protein was mainly localized in astrocytes, but was present in neurons in the subfornical organ. Intracerebroventricular (ICV) injection of human REN (hREN) in conscious unrestrained mice elicited a pressor response, which was abolished by ICV preinjection of losartan. Double-transgenic mice expressing the hREN gene and the GFAP-hAGT transgene exhibited a 15–mm Hg increase in blood pressure and an increased preference for salt. Blood pressure in the hREN/GFAP-hAGT mice was lowered after ICV, but not intravenous losartan. These studies suggest that AGT synthesis in the brain has an important role in the regulation of blood pressure and electrolyte balance.