Key result
PAH-RVH was associated with significantly lower cardiac output (58.3 vs 82.9 mL/min; P<0.001) and treadmill distance (41.5 vs 244.1 m; P<0.001) compared to PAB-RVH.
Why the study?
Does inhibiting Gβγ-GRK2 interactions or using dobutamine improve inotropic reserve in right ventricular hypertrophy?
Does inhibiting Gβγ-GRK2 interactions or using dobutamine improve inotropic reserve in right ventricular hypertrophy?
Absolute Event Rate: 58.3% vs 82.9%
p-value: p=<0.001
GRK2-mediated desensitization of adrenergic and dopaminergic receptors impairs inotropic reserve in PAH-RVH, suggesting dobutamine is superior to dopamine for acute inotropic support and highlighting GRK2 inhibition as a potential therapeutic target.
GRK2 desensitization may limit inotropy in PAH-RVH; leaves open whether inhibition or dobutamine improves human right heart failure.
BACKGROUND: The cause and consequences of impaired adrenergic signaling in right ventricular failure/hypertrophy (RVH) are poorly understood. We hypothesized that G protein-coupled receptor kinase-2 (GRK2)-mediated uncoupling of β-adrenergic receptor signaling impairs inotropic reserve. The implications of right ventricular (RV) adrenergic remodeling for inotrope selection and the therapeutic benefit of interrupting Gβγ-GRK2 interaction, using gallein, were tested. METHODS AND RESULTS: Chamber-specificity and cellular localization of adrenergic remodeling were compared in rodent RVH associated with pulmonary arterial hypertension (PAH-RVH; SU5416+chronic-hypoxia or Monocrotaline) versus pulmonary artery banding-induced RVH (PAB-RVH). Results were corroborated in RV arrays from 10 PAH patients versus controls. Inotropic reserve was assessed in RV- and left ventricular-Langendorff models and in vivo. Gallein therapy (1.8 mg/kg/day ×2-weeks) was assessed. Despite similar RVH, cardiac output (58.3±4.9 versus 82.9±4.8 mL/min; P<0.001) and treadmill distance (41.5±11.6 versus 244.1±12.4 m; P<0.001) were lower in PAH-RVH versus PAB-RVH. In PAH-RVH versus PAB-RVH there was greater downregulation of β1-, α1- and dopamine-1 receptors, more left ventricular involvement, and greater impairment of RV contractile reserve. RV GRK2 activity increased in parallel with a reduction in both adrenergic receptor expression and inotrope-stimulated cAMP levels (P<0.01). β1-receptor downregulation also occurred in human PAH-RVH. Dobutamine was superior to dopamine as an RV inotrope, both ex vivo and in vivo. CONCLUSIONS: GRK2-mediated desensitization-downregulation of adrenergic and dopaminergic receptors impairs inotropic reserve in PAH-RVH. Acute inotropic support in RVH is best accomplished by dobutamine, reflecting its better coupling to adenylyl cyclase and the reliance of dopamine on dopamine-1-receptor signaling, which is impaired in RVH. Inhibiting Gβγ-GRK2 interactions has therapeutic benefit in RVH.
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Piao et al. (2012) studied Right ventricular hypertrophy (RVH) associated with pulmonary arterial hypertension (PAH). PAH-RVH vs. PAB-RVH was evaluated on Cardiac output (mL/min) (p=<0.001). PAH-RVH was associated with significantly lower cardiac output (58.3 vs 82.9 mL/min; P<0.001) and treadmill distance (41.5 vs 244.1 m; P<0.001) compared to PAB-RVH.
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