Abstract 14444: H11 Kinase Interacts Predominantly with Phospho p38MAPK as Compared to Phospho Akt in Cytosol of Failing Left Ventricular Myocardium of Dogs with Chronic Heart Failure
Background: H11 kinase (H11K) plays a dual role by conferring cardioprotection against ischemia/reperfusion injury through activation of Akt-signaling and by triggering cardiomyocyte apoptosis via activation p38MAPK. The mechanism underlying this dual nature of H11K signaling is not fully understood. We and others have previously shown increased H11K-expression level in LV myocardium of failed human hearts and hearts from dogs with coronary microembolization-induced heart failure (HF). We also reported that increased H11K protein level in the dog failing LV tissue was observed in cytosolic fraction but it was decreased in nuclear fraction. In this study, we demonstrate for the first time that in failing LV myocardium, cytosolic H11K interacts predominantly with phosphorylated (p)-p38MAPK but least with p-Akt.
Methods: Cytosolic fraction was prepared from LV tissue of 3 dogs with HF (LV ejection fraction ∼25%) and 3 normal (NL) dogs. Using primary antibody, H11K was immuno-precipitated from cytosolic proteins. Using Western blotting coupled with chemiluminescent method, p-Akt and p-p38MAPK were probed in the resulting H11K-immunoprecipitate and the band density was quantified using a Biorad densitometer and expressed in densitometric units (du).
Results: In the H11K immunoprecipated fraction, p-Akt protein level was significantly reduced in failing LV myocardium compared to NL LV (0.34 ± 0.10 vs. 0.99 ± 0.14 du, p<0.05). In contrast, p-P38MAPK protein level was increased significantly in failing LV myocardium compared to LV NL dogs (0.74 ± 0.10 vs. 0.29 ± 0.14 du, p<0.05 vs. NL) .
Conclusion: Increased cytosolic H11K protein in the failing LV interacts predominantly with p-p38MAPK but least with p-Akt. These observations suggest the possibility that therapies that restore interaction of H11K with p-Akt may be useful in the partially reversing the progression of LV dysfunction characteristic of the HF state.
- © 2012 by American Heart Association, Inc.