Protein kinase Cα, but not PKCβ or PKCγ, regulates contractility and heart failure susceptibility: implications for ruboxistaurin as a novel therapeutic approach

Q Liu, X Chen, SM MacDonnell, EG Kranias… - Circulation …, 2009 - Am Heart Assoc
Q Liu, X Chen, SM MacDonnell, EG Kranias, JN Lorenz, M Leitges, SR Houser…
Circulation research, 2009Am Heart Assoc
Protein kinase (PK) Cα, PKCβ, and PKCγ comprise the conventional PKC isoform subfamily,
which is thought to regulate cardiac disease responsiveness. Indeed, mice lacking the gene
for PKC α show enhanced cardiac contractility and reduced susceptibility to heart failure.
Recent data also suggest that inhibition of conventional PKC isoforms with Ro-32-0432 or
Ro-31-8220 enhances heart function and antagonizes failure, although the isoform
responsible for these effects is unknown. Here, we investigated mice lacking PKC α, PKC β …
Protein kinase (PK)Cα, PKCβ, and PKCγ comprise the conventional PKC isoform subfamily, which is thought to regulate cardiac disease responsiveness. Indeed, mice lacking the gene for PKCα show enhanced cardiac contractility and reduced susceptibility to heart failure. Recent data also suggest that inhibition of conventional PKC isoforms with Ro-32-0432 or Ro-31-8220 enhances heart function and antagonizes failure, although the isoform responsible for these effects is unknown. Here, we investigated mice lacking PKCα, PKCβ, and PKCγ for effects on cardiac contractility and heart failure susceptibility. PKCα−/− mice, but not PKCβγ−/− mice, showed increased cardiac contractility, myocyte cellular contractility, Ca2+ transients, and sarcoplasmic reticulum Ca2+ load. PKCα−/− mice were less susceptible to heart failure following long-term pressure-overload stimulation or 4 weeks after myocardial infarction injury, whereas PKCβγ−/− mice showed more severe failure. Infusion of ruboxistaurin (LY333531), an orally available PKCα/β/γ inhibitor, increased cardiac contractility in wild-type and PKCβγ−/− mice, but not in PKCα−/− mice. More importantly, ruboxistaurin prevented death in wild-type mice throughout 10 weeks of pressure-overload stimulation, reduced ventricular dilation, enhanced ventricular performance, reduced fibrosis, and reduced pulmonary edema comparable to or better than metoprolol treatment. Ruboxistaurin was also administered to PKCβγ−/− mice subjected to pressure overload, resulting in less death and heart failure, implicating PKCα as the primary target of this drug in mitigating heart disease. As an aside, PKCαβγ triple-null mice showed no defect in cardiac hypertrophy following pressure-overload stimulation. In conclusion, PKCα functions distinctly from PKCβ and PKCγ in regulating cardiac contractility and heart failure, and broad-acting PKC inhibitors such as ruboxistaurin could represent a novel therapeutic approach in treating human heart failure.
Am Heart Assoc