Antisense Inhibition of the Brain Kallikrein-Kinin System

Abstract

We used antisense oligodeoxynucleotide (ODN) strategy, based on interference of information flow from gene to protein, to determine the role of kininogen and bradykinin B 2 receptor genes in the pathogenesis of genetic hypertension in rats. Mean blood pressure of 9-week-old spontaneously hypertensive rats (SHR) increased 4 hours after acute intracerebroventricular injection of synthetic 18-mer antisense ODNs targeting the translation initiation codon of kininogen mRNA (from 164±5 to 181±4 mm Hg, P <.01) or bradykinin B 2 receptor mRNA (from 161±5 to 185±8 mm Hg, P <.01) and then returned to basal levels within 24 hours. Prolonged vasopressor effects were observed after repeated injections of antisense ODN targeting kininogen mRNA. Antisense ODNs to kininogen and B 2 receptor mRNAs increased blood pressure of normotensive Wistar-Kyoto rats only slightly compared with SHR (from 116±3 to 124±1 and from 116±2 to 126±4 mm Hg, respectively; P <.05). Cardiovascular responses were confirmed by the use of antisense ODNs targeted to bind to different nonoverlapping regions of kininogen or B 2 receptor mRNA. Microinjection of antisense ODN to B 2 receptor mRNA into the nucleus tractus solitarii increased mean blood pressure in SHR and prevented the vasodepressor effect induced by intranuclear microinjection of bradykinin. No significant change in mean blood pressure was induced in either strain by intravenous injection of antisense ODNs or by central injection of sense or scrambled ODNs. A strong fluorescent signal was detected at the level of the hippocampus, thalamus, hypothalamus periventricularis, midbrain, and cerebrum 1 hour after central injection of fluorescein isothiocyanate–conjugated antisense ODNs. Kininogen levels were significantly lower in the brain of rats given intracerebroventricular antisense kininogen ODN compared with controls. Our results indicate that the brain kallikrein-kinin system plays a role in the central regulation of blood pressure and suggest that this system may exert a protective action against further elevations of blood pressure levels in SHR.