Intracardiac Injection of AdGRK5-NT Reduces Left Ventricular Hypertrophy by Inhibiting NF-κB–Dependent Hypertrophic Gene Expression

Abstract

Abstract-Several studies underline the role of the transcription factor NF-B in the development of left cardiac hypertrophy (LVH). We have demonstrated recently that the RGS homology domain within the amino terminus of GRK5 (GRK5-NT) is able to inhibit NF-B transcription activity and its associated phenotypes. The aim of this study was to evaluate the ability of GRK5-NT to regulate LVH through the inhibition of NF-B both in vitro and in vivo. In cardiomyoblasts, GRK5-NT inhibits phenylephrine-induced transcription of both NF-B and atrial natriuretic factor promoters, assessed by luciferase assay, thus confirming a role for this protein in the regulation of cardiomyocyte hypertrophy. In vivo, we explored 2 rat models of LVH, the spontaneously hypertensive rat and the normotensive Wistar Kyoto rat exposed to chronic administration of phenylephrine. Intracardiac injection of an adenovirus encoding for GRK5-NT reduces cardiac mass in spontaneously hypertensive rats and prevents the development of phenylephrineinduced LVH in Wistar Kyoto rats. This associates with inhibition of NF-B signaling (assessed by NF-B levels), transcriptional activity and phenotypes (fibrosis and apoptosis). Such phenomenon is independent from hemodynamic changes, because adenovirus encoding for GRK5-NT did not reduce blood pressure levels in spontaneously hypertensive rats or in Wistar Kyoto rats. In conclusion, our study supports the regulation of LVH based on the GRK5-NT inhibition of the NF-B transduction signaling. (Hypertension. 2010;56:696-704.)Key Words: cardiac hypertrophy Ⅲ intracardiac injection Ⅲ spontaneously hypertensive rats Ⅲ NF-B Ⅲ transcription factors N F-B is an ubiquitously expressed transcription factor that modulates the expression of genes involved in the regulation of cell functions, such as survival, apoptosis, growth, division, innate immunity, differentiation, and cellular responses to stress, hypoxia, and ischemia. 1-4 The classic cellular model in which this factor is studied is the immune system for its central role in cytokine production. 4,5 It has been reported recently that NF-B is relevant in the development of left ventricular hypertrophy (LVH) and remodeling through mechanisms independent from inflammation. NF-B mediates hypertrophic growth of cardiomyocytes in response to G protein-coupled receptor agonists, including norepinephrine, endothelin 1, and angiotensin II. 6,7 Also, NF-B inhibition attenuates LVH in different animal models of disease. 8,9 This evidence suggests that NF-B blockade may be an effective strategy to inhibit LVH and remodeling. The family of G protein-coupled receptor kinases (GRKs) and, in particular GRK2 and GRK5, possesses the ability to bind both NF-B and its inhibitor, IB␣. 10,11 In particular, GRK5, by means of its RGS homology (RH) domain within the amino terminus, interacts with IB␣ leading to the stabilization and accumulation of the IB␣/NF-B complex in the nucleus and, consequently, to the inhibition of NF-B transcriptional activity. 11 This feature of the RH domain of GR...

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“…Real-time quantitative reverse-transcriptase-PCR (RT-qPCR) was performed as described (75,76). In brief, total RNA was isolated using TRIzol reagent (Thermo Fisher Scientific) in combination with the RNeasy Mini kit (QIAGEN) followed by DNase treatment, and cDNA was synthesized by means of a Thermo-Script RT-PCR System (Thermo Fisher Scientific), according to the manufacturer's instruction.…”

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