Abstract 8840: P21-Activated Kinase Improves Myocardial Performance through Modulation of Troponin-T and Myosin Light Chain 2 during Global Myocardial Ischemia and Reperfusion Injury
Emerging evidence indicates a role for p21-activated kinase (Pak1) in ischemia/reperfusion (I/R), but it is not clear whether Pak1 activation during ischemia reduces or increases injury. We hypothesize that activation of the Pak1 signaling pathway activates NADPH oxidase and induces post-translational modifications in myofilament proteins, which promote cardioprotective mechanisms that prevent or reverse the detrimental effects of ischemic injury in mouse cardiac tissue. We subjected ex vivo hearts from WT (wild type, n=9) and Pak1-KO (knock-out, n=16) mice to 20 minutes of global ischemia followed by 30 minutes of reperfusion. Percent recovery of the left ventricular developed pressure (LVDP) after I/R injury (LVDP after I/R divided by the LVDP before ischemia) in Pak1-KO hearts was significantly reduced (37.6 ± 4.9%) compared to WT (49.9 ± 2.2%). End systolic pressure was significantly reduced after I/R injury in both WT (85.6 ± 1.7 before I/R to 69.8 ± 1.8 mmHg after I/R) and Pak1-KO hearts (90.8 ± 3.7 to 68.8 ± 3.2 mmHg after I/R), but was not significantly different between WT and Pak1-KO hearts. However, ANOVA revealed end diastolic pressure was significantly increased in Pak1-KO hearts during reperfusion, compared to WT controls. ProQ analysis showed TnT phosphorylation was increased at baseline in Pak1-KO hearts compared to WT, and increased in WT after I/R, but did not increase in Pak1-KO hearts after I/R. MLC2 phosphorylation was significantly decreased in Pak1-KO hearts compared to WT after I/R injury. The current study has advanced the field by demonstrating for the first time that Pak1 and p47phox establish a protein-protein interaction in left ventricular cardiac tissue as assessed by co-immunoprecipitation, and that Pak1 co-localizes with p47phox and p22phox in the adult mouse cardiac myocyte, as assessed by immunofluorescence. Additionally, Pak1 signaling acts upon myofilament proteins and is beneficial during I/R injury, in that Pak1 reduces end diastolic pressure and increases left ventricular developed pressure after I/R injury. Thus, the current study provides a novel pathway including the targets Pak1, p47phox, TnT, and MLC2 for development of pharmaceutical interventions for use in the clinic for patients with ischemic events.
- © 2011 by American Heart Association, Inc.