Level of G protein–Coupled Receptor Kinase-2 Determines Myocardial Ischemia/Reperfusion Injury via Pro- and Anti-Apoptotic Mechanisms

Abstract

Rationale: Activation of prosurvival kinases and subsequent nitric oxide (NO) production by certain G protein-coupled receptors (GPCRs) protects myocardium in ischemia/reperfusion injury (I/R) models. GPCR signaling pathways are regulated by GPCR kinases (GRKs), and GRK2 has been shown to be a critical molecule in normal and pathological cardiac function.Objective: A loss of cardiac GRK2 activity is known to arrest progression of heart failure (HF), at least in part by normalization of cardiac ␤-adrenergic receptor (␤AR) signaling. Chronic HF studies have been performed with GRK2 knockout mice, as well as expression of the ␤ARKct, a peptide inhibitor of GRK2 activity. This study was conducted to examine the role of GRK2 and its activity during acute myocardial ischemic injury using an I/R model. Methods and Results:We demonstrate, using cardiac-specific GRK2 and ␤ARKct-expressing transgenic mice, a deleterious effect of GRK2 on in vivo myocardial I/R injury with ␤ARKct imparting cardioprotection. Post-I/R infarct size was greater in GRK2-overexpressing mice (45.0؎2.8% versus 31.3؎2.3% in controls) and significantly smaller in ␤ARKct mice (16.8؎1.3%, P<0.05). Importantly, in vivo apoptosis was found to be consistent with these reciprocal effects on post-I/R myocardial injury when levels of GRK2 activity were altered. Moreover, these results were reflected by higher Akt activation and induction of NO production via ␤ARKct, and these antiapoptotic/survival effects could be recapitulated in vitro. Interestingly, selective antagonism of ␤ 2 ARs abolished ␤ARKct-mediated cardioprotection, suggesting that enhanced GRK2 activity on this GPCR is deleterious to cardiac myocyte survival. Conclusion:The novel effect of reducing acute ischemic myocardial injury via increased Akt activity and NO production adds significantly to the therapeutic potential of GRK2 inhibition with the ␤ARKct not only in chronic HF but also potentially in acute ischemic injury conditions. (Circ Res. 2010;107:1140-1149.) Key Words: acute myocardial ischemia Ⅲ ischemia/reperfusion injury Ⅲ cardioprotection Ⅲ G protein-coupled receptor kinase-2 Ⅲ ␤ARKct Ⅲ myocyte apoptosis

MicroRNA-133 Modulates the β 1 -Adrenergic Receptor Transduction Cascade

“…In line with this, Tg133 mice at 1 week after TAC showed reduced levels of the β 1 but not β 2 -adrenergic receptor kinase (G protein-coupled receptor kinases 2 and 3, respectively; Figure 6D; Online Figure IVD), which has previously been shown to exert a prodeath function. 33 Likewise, also the mRNA levels of identified miR-133 targets were downregulated in Tg133 mice after TAC ( Figure 5B; Online Figure VIA).…”

Involvement of Nuclear Factor κB (NF-κB) Signaling Pathway in Regulation of Cardiac G Protein-coupled Receptor Kinase 5 (GRK5) Expression

“…Maintenance of Primary Culture, Immunoblot Analysis, and Total Cellular Lysate Preparation-Ventricular cardiomyocytes from 1-to 2-day-old rat neonatal hearts (NRVMs) were prepared, as we have published recently (18). Myocytes were cultured in Ham's F-10 supplemented with penicillin/streptomycin (100 units/ml) and 5% FBS at 37°C in 5% CO 2 humidified atmosphere for 2-3 days.…”

Regulation of Nuclear Factor κB (NF-κB) in the Nucleus of Cardiomyocytes by G Protein-coupled Receptor Kinase 5 (GRK5)

“…In the heart, GRK2 and GRK5 are the most abundant, and importantly, both have been shown to be up-regulated in failing human myocardium (1,4). Animal models have led to the discovery that when GRK2 and GRK5 are elevated in the heart, they can drive pathological signaling and heart failure (HF) (5)(6)(7)(8).…”