Proteasome degradation of GRK2 during ischemia and ventricular tachyarrhythmias in a canine model of myocardial infarction

Abstract

Arrhythmia-prone subepicardial border zone (EBZ) tissue demonstrates decreased G protein receptor kinase 2 (GRK2) activity and increased sensitivity to isoproterenol 6 -24 h after coronary artery ligation (CAL) in the dog. With the use of a semiquantitative immunofluorescence technique, the relative fluorescence intensity (RF) of GRK2 in EBZ decreased to 24% of that in a remote site (RS) (P Ͻ 0.01, n ϭ 30 cells from 3 dogs), whereas GRK5 RF did not change. Confocal studies of cardiac tissue from transgenic mice overexpressing GRK2 validated the use of a semilogarithmic relationship between RF and GRK2 activity. As shown with the use of quantitative real-time RT-PCR, both GRK2 and GRK5 mRNA were not decreased at 24 h in EBZ (n ϭ 6 dogs) relative to RS control, indicating that the decrease of GRK2 in the EBZ is likely due to posttranscriptional degradation following CAL. Pretreatment of six dogs with the selective proteasome inhibitor bortezomib provided 100% (EBZ) and 50% (infarct) protection against loss of GRK2 at 24 h. There was an absence of rapid (Ͼ300 beats/min) and very rapid (Ͼ360 beats/min) ventricular triplets that are highly predictive of sudden cardiac death during ECG monitoring in the bortezomib-pretreated animals in contrast to nonpretreated infarcted animals. We have demonstrated that the dramatic decrease in GRK2 in cardiac ischemic tissue can be largely blocked by prior proteasome blockade and that this is associated with significant cardioprotection against malignant ventricular tachyarrhythmias.

Unexpected cardiotoxicity in haematological bortezomib treated patients

“…Additionally, although bortezomib was found to reduce the onset of delayed arrhythmias following coronary ligation in the canine model by upregulating correspondence the adrenergic sensitiser GRK2 (Yu et al, 2005), in the absence of an acute ischaemic event this mechanism may rather be responsible for deleterious cardiac effects (Liu et al, 2005). Indeed, desensitisation of the adrenergic receptor, while preventing tachyarrhythmias (Liu et al, 2005) might potentially favour bradycardia, as accordingly shown in our population.…”

Analyses on Activation of NF-κB and Effect of Bortezomib in Canine Neoplastic Lymphoid Cell Lines

“…Thus, bortezomib may be applicable to treatment for canine clinical cases with lymphoid malignancies. A previous study showed that 0.2 mg/kg was the maximal tolerated dosage of bortezomib for dogs [21]. And, another study mentioned that 10 ng/ml of bortezomib supplemented to culturing cell lines was nearly corresponding to the clinical dose used in humans [11].…”

Regulation of the proteasome by ATP: implications for ischemic myocardial injury and donor heart preservation

“…Nevertheless, in vivo inhibition of the proteasome by PS-519 and bortezomib was confirmed using whole blood or leukocyte proteasome peptidase activity measurements as a surrogate for their pharmacological efficacy in some studies (67,117,150). Furthermore, the basic arginine/ proline-rich peptide PR-39 has been reported to prevent proteasome-mediated degradation of IB␣ without effects on proteasomal degradation of total cellular protein (10,44).…”

“…It should be noted, however, that the majority of these studies did not assess myocardial ATP content or cardiac proteasome activities (10,21,44,67,91,99,116,117,131,150); proteasome inhibitors were employed based on their anti-inflammatory ( (91,146) or to assess whether they affect G protein receptor kinase 2 (GRK2) expression during ischemia (67,150). Nevertheless, in vivo inhibition of the proteasome by PS-519 and bortezomib was confirmed using whole blood or leukocyte proteasome peptidase activity measurements as a surrogate for their pharmacological efficacy in some studies (67,117,150).…”