Hata Jonathan A, Williams Matthew L, Schroder Jacob N, Lima Brian, Keys Janelle R, Blaxall Burns C, Petrofski Jason A, Jakoi Andre, Milano Carmelo A, Koch Walter J
Department of Surgery, Duke University Medical Center, Durham, North Carolina, USA.
J Card Fail. 2006 Jun;12(5):360-8. doi: 10.1016/j.cardfail.2006.02.011.
In human heart failure, increased expression of G protein-coupled receptor kinases (GRKs) causes the loss of beta-adrenergic receptor (betaAR) signaling and function. Mechanical unloading with a left ventricular assist device (LVAD) promotes reverse remodeling, which includes restoration of betaAR responsiveness. We tested the hypothesis that LVAD support of the failing human heart alters the expression and activity of GRKs and we sought to determine whether changes in myocardial GRKs could be tracked in lymphocytes.
Paired samples of human LV tissue (n = 12) and blood were obtained at the time of LVAD implantation (heart failure) and subsequent cardiac transplantation (LVAD). betaAR signaling was quantified by receptor density and adenylyl cyclase activity. Immunoblotting and real-time reverse transcription polymerase chain reaction were used to measure GRK2 and GRK5 protein and mRNA levels. Rhodopsin phosphorylation was used to assess total GRK activity. Consistent with reverse remodeling, betaAR density and signaling were restored to nonfailing levels after LVAD support. GRK2 protein levels were significantly reduced 55% after LVAD support and GRK2 mRNA was similarly reduced. In contrast, GRK5 protein and mRNA levels were unchanged. Total myocardial GRK activity was reduced similar to the drop in GRK2 expression. In lymphocytes, GRK2 protein levels were decreased after LVAD support and there was a significant positive correlation between myocardial and lymphocyte GRK2 levels in both heart failure and LVAD samples.
The changes in myocardial GRK2 expression and activity that are mirrored in lymphocytes provide a possible mechanism for the restoration of betaAR signaling and reverse remodeling after mechanical unloading in the failing heart. Moreover, lymphocytes may provide a surrogate marker of myocardial GRK2 in these patients.
在人类心力衰竭中，G蛋白偶联受体激酶（GRKs）表达增加导致β-肾上腺素能受体（βAR）信号传导和功能丧失。使用左心室辅助装置（LVAD）进行机械卸载可促进逆向重构，其中包括βAR反应性的恢复。我们检验了以下假设：LVAD对衰竭人类心脏的支持会改变GRKs的表达和活性，并试图确定是否可以在淋巴细胞中追踪心肌GRKs的变化。
在植入LVAD（心力衰竭）及随后的心脏移植（LVAD）时获取成对的人类LV组织样本（n = 12）和血液样本。通过受体密度和腺苷酸环化酶活性对βAR信号传导进行定量。采用免疫印迹和实时逆转录聚合酶链反应来测量GRK2和GRK5蛋白及mRNA水平。视紫红质磷酸化用于评估总GRK活性。与逆向重构一致，LVAD支持后βAR密度和信号传导恢复至非衰竭水平。LVAD支持后GRK2蛋白水平显著降低55%，GRK2 mRNA也有类似降低。相比之下，GRK5蛋白和mRNA水平未发生变化。总的心肌GRK活性降低，与GRK2表达下降相似。在淋巴细胞中，LVAD支持后GRK2蛋白水平降低，在心力衰竭和LVAD样本中，心肌和淋巴细胞GRK2水平之间均存在显著正相关。
淋巴细胞中反映出的心肌GRK2表达和活性变化为衰竭心脏机械卸载后βAR信号传导恢复和逆向重构提供了一种可能机制。此外，淋巴细胞可能是这些患者中心肌GRK2的替代标志物。
