¹Center for Translational Medicine and George Zallie and Family Laboratory for Cardiovascular Gene Therapy, Department of Medicine, Thomas Jefferson University, Philadelphia, Pennsylvania, USA

Correspondence: Walter J. Koch, Center for Translational Medicine, George Zallie and Family Laboratory for Cardiovascular Gene Therapy, Thomas Jefferson University, 1025 Walnut Street, Room 317, Philadelphia, Pennsylvania 19107, USA. E-mail: Walter.koch@jefferson.edu

The first two authors contributed equally to this work.

Received 5 July 2007; Accepted 29 October 2007; Published online 27 November 2007.

Abstract

We recently reported that the upregulation of adrenal G protein–coupled receptor kinase-2 (GRK2) causes enhanced catecholamine (CA) secretion by desensitizing sympatho-inhibitory ₂-adrenergic receptors ( ₂ARs) of chromaffin cells, and thereby aggravating heart failure (HF). In this study, we sought to develop an efficient and reproducible in vivo adrenal gene transfer method to determine whether manipulation of adrenal GRK2 levels/activity regulates physiological CA secretion in rats. We specifically investigated two different in vivo gene delivery methods: direct injection into the suprarenal glands, and retrograde delivery through the suprarenal veins. We delivered adenoviral (Ad) vectors containing either GRK2 or an inhibitor of GRK2 activity, the ARKct. We found both delivery approaches equally effective at supporting robust (>80% of the whole organ) and adrenal-restricted transgene expression, in the cortical region as well as in the medullar region. Additionally, rats with AdGRK2-infected adrenals exhibit enhanced plasma CA levels when compared with control rats (AdGFP-injected adrenals), whereas plasma CA levels after Ad ARKct infection were significantly lower. Finally, in isolated chromaffin cells, ₂ARs of AdGRK2-infected cells failed to inhibit CA secretion whereas Ad ARKct-infected cells showed normal ₂AR responsiveness. These results not only indicate that in vivo adrenal gene transfer is an effective way of manipulating adrenal gland signalling, but also identify GRK2 as a critically important molecule involved in CA secretion.