Targeted inhibition of calcineurin attenuates cardiac hypertrophy in vivo

Abstract

The Ca 2؉ -calmodulin-activated Ser͞Thr protein phosphatase calcineurin and the downstream transcriptional effectors of calcineurin, nuclear factor of activated T cells, have been implicated in the hypertrophic response of the myocardium. Recently, the calcineurin inhibitory agents cyclosporine A and FK506 have been extensively used to evaluate the importance of this signaling pathway in rodent models of cardiac hypertrophy. However, pharmacologic approaches have rendered equivocal results necessitating more specific or genetic-based inhibitory strategies. In this regard, we have generated Tg mice expressing the calcineurin inhibitory domains of Cain͞Cabin-1 and A-kinase anchoring protein 79 specifically in the heart. ⌬Cain and ⌬A-kinase-anchoring protein Tg mice demonstrated reduced cardiac calcineurin activity and reduced hypertrophy in response to catecholamine infusion or pressure overload. In a second approach, adenoviral-mediated gene transfer of ⌬Cain was performed in the adult rat myocardium to evaluate the effectiveness of an acute intervention and any potential species dependency. ⌬Cain adenoviral gene transfer inhibited cardiac calcineurin activity and reduced hypertrophy in response to pressure overload without reducing aortic pressure. These results provide genetic evidence implicating calcineurin as an important mediator of the cardiac hypertrophic response in vivo.C ardiac hypertrophy is broadly defined as an adaptive enlargement of the myocardium characterized by the growth of individual cardiac myocytes rather than an increase in cell number. Whereas cardiac hypertrophy is a beneficial response that temporarily augments output, sustained hypertrophy often becomes maladaptive and is a leading predictor of future heart failure (1, 2). To understand the molecular mechanisms that underlie adaptive and maladaptive cardiac hypertrophy, investigation has centered around a characterization of the intracellular signal transduction pathways that promote cardiac myocyte growth (3, 4).One such intracellular signaling pathway involves the calciumcalmodulin, Ser͞Thr protein phosphatase calcineurin (PP2B). Sustained elevations in intracellular calcium concentration, in association with calmodulin, directly activate calcineurin phosphatase activity leading to the dephosphorylation and nuclear translocation of a family of transcription factors known as nuclear factor of activated T cells (5, 6).A role for calcineurin and nuclear factor of activated T cells as regulators of cardiac hypertrophy was recently identified (7). Transgenic (Tg) mice expressing an activated calcineurin or a constitutively nuclear nuclear factor of activated T cells c4 factor in the heart demonstrated profound hypertrophy that rapidly progressed to heart failure (7). In vitro, adenoviral-mediated gene transfer of activated calcineurin also promoted hypertrophic growth of neonatal cardiac myocytes (8). Treatment of cultured cardiomyocytes with the calcineurin inhibitory agents cyclosporine A (CsA) or FK506 blocked agonist-induced hypertrop...

Targeted Inhibition of Calcineurin in Pressure-overload Cardiac Hypertrophy

“…neural) effects of calcineurin suppression. Similar results were recently reported using other transgenic approaches (14,15).…”

“…This unexpected finding suggests that activation of ANF expression is not directly dependent on calcineurin activity but rather occurs prior to or in parallel with calcineurin signaling. It is n ϭ 11 n ϭ 9 n ϭ 9 Diastole (14) expressed calcineurin inhibitory domains from two different proteins and observed significant attenuation of hypertrophic marker changes. At this point, we do not know why fetal gene expression is different in the MCIP1 TAB mice compared with these other models, even though attenuation of hypertrophy was similar.…”

The SCF Cdc4 ubiquitin ligase regulates calcineurin signaling through degradation of phosphorylated Rcn1, an inhibitor of calcineurin

“…Precise regulation of calcineurin is important for a proper response to Ca 2ϩ signals. Aberrant calcineurin activity results in various disorders, such as osteoporosis (2), cardiac hypertrophy (3,4) and Down's syndrome (5,6). The mechanism responsible for activation of calcineurin in response to Ca 2ϩ signals appears to be conserved from human to yeast.…”

Direct monitoring pressure overload predicts cardiac hypertrophy in mice

“…Cardiac hypertrophy, fibrosis and gene expression changes are all consequences of POL, a commonly used animal model for cardiovascular research (Rockman et al 1991, De Windt et al 2001, Asakawa et al 2002, McMullen et al 2003, Liao et al 2004, De Acetis et al 2005, Takimoto et al 2005. However, their correlations with direct measurements of hemodynamic parameters in POL have not been determined in conscious ambulatory mice.…”

“…Abdominal aortic constriction (De Windt et al 2001, Wettschureck et al 2001 was performed to induce pressure overload in mice. Briefly, the mice were anesthetized with 2% isoflurane inhalation and midline abdominal incisions were made to expose the abdominal aortas.…”