Heart failure (HF) is a progressive disease with rapidly increasing rates of morbidity and mortality; it is the leading cause of death worldwide. Elevated sympathetic nervous system activity, a salient feature of HF progression, leads to pathologic attenuation and desensitization of β-adrenergic receptors (β-ARs) due in part to Gβγ-mediated signaling. We recently reported that novel small molecule Gβγ inhibitors selectively block specific Gβγ signals and halt HF progression in pharmacologic and transgenic mouse models of HF.
We assessed the
hypothesis
that the Gβγ inhibitor Gallein could be salutary in treating pre-existing HF in a clinically relevant model.
We utilized the pressure-overload HF model of mouse transverse aortic constriction (TAC). Four weeks post-TAC, mice received daily IP injections of vehicle (PBS; group V) or Gallein (10mg/Kg/day; group G) for eight weeks. Gallein treatment improved survival (7 of 9 mice survived vs. 5 of 9 mice in group V) and cardiac function (%EF 75.2 ± 7.5 vs 35.6 ± 17.2 in group V, +dP/dt (mmHg/sec) 7022 ± 485.3 vs. 3584 ± 598.6 in group V), -dP/dt (mmHg/sec) -5826 ± 910.7 vs. -3260 ± 62.3 in group V, LVEDP (mmHg) 11.5 ± 3.7 vs. 29.45 ± 3.6 in group V). In addition, gallein reduced cardiac hypertrophy (HW/BW (mg/g) 5.8 ± 0.3 vs. 8.8 ± 1.1 in group V) and plasma catecholamine concentrations (adrenaline (ng/ml) 1.3 ± 0.3 vs. 6.6 ± 2.8 in group V, noradrenaline (ng/ml) 3.6 ± 0.6 vs. 15.1 ± 3.6 in group V). Reduction of interstitial fibrosis as well as mRNA levels of α-SMA, TNF-α, and IL-6 was observed in the hearts of Gallein treated animals (59.7 ± 14.1%, 43.8 ± 9.3% and 28.5 ± 3.5% relative to group V, respectively). On the molecular level, Gallein treated mice showed less GRK2 and PI3Kγ membrane recruitment, and less Akt activation (42.9 ± 7.1%, 66.7 ± 13.3% and 46.2 ± 7.7% relative to group V, respectively) in myocardial lysates.
In
conclusion
, these data suggest a possible therapeutic role for small molecule Gβγ inhibition in halting the progression of HF, potentially via inhibition of the Gβγ-GRK2-PI3Kγ-Akt pathway. The combined effect of halting HF progression and reducing plasma catecholamines suggests a possible systemic role for small molecule Gβγ inhibition in both the heart and the adrenal gland.
Effect of ACE inhibitor on blood plasma catecholamine concentration.The study in a mild essential hypertension patient and a rabbit.
