Abstract 17041: Attenuating the Interaction Between Delta PKC (dPKC) and the d Subunit of F1Fo ATP Synthase (dF1Fo) protects Against Myocardial Infarction in Rats
Our laboratory previously, developed a mitochondrially-targeted peptide inhibitor [NH2-YGRKKRRQRRRMLATRALSLIGKRAISTSVC-COOH] of the dPKC-dF1Fo interaction that improves contractility and energetics, and reduces infarction following ischemia / reperfusion (IR) injury in perfused rat hearts. In the present study we tested the hypothesis that dPKC inhibits ATP production in vivo via an interaction with dF1Fo to exacerbate cardiac IR injury. In rats administered the dPKC-dF1Fo inhibitor (5 ug/kg) intravenously (I.V.) for 20 min, we observed substantial FLAG immunoreactivity (The dPKC-dF1Fo inhibitor is tagged with a FLAG epitope) in cardiac subsarcolemmal (SSM) and interfibrillar (IFM) mitochondria (n=6, p<0.03 and p<0.006). In rats receiving a 10 min coronary occlusion we observed a 5-fold induction of dPKC-dF1Fo co-immunoprecipitation (co-IP) in the left ventricular (LV) region at risk (RAR) for ischemia). This was reduced by 71 +/- 13 %,( p<0.001, n=8) in rats receiving the dPKC-dF1Fo inhibitor I.V. In addition, dPKC-phosphoserine 643 immunoreactivity (a dPKC autophosphorylation site) in RAR mitochondria was elevated by 56 +/- 17% (n=7, p<0.01) over that in non-ischemic (LV region not at risk (RNAR)) mitochondria. The dPKC-dF1Fo inhibitor also reduced infarction in the RAR as assessed by 2,3,5-triphenyltetrazolium chloride staining by 29 +/- 7 % n=6, p<0.001). This protection was correlated with a 1.7 +/- 0.2-fold (n=6, p<0.02) enhancement of ATP levels in the LV RAR and a 61 +/- 12 % (n=8), p<0.001) reduction in Ca++-induced mitochondrial swelling in ischemic myocardium. The dPKC-dF1Fo inhibitor also transiently elevated levels of beta-tubulin (42 +/- 8 % (n=8), p<0.001) and the number IV subunit of cytochrome oxidase (64 +/- 9 % (n=8), p<0.05) following brief ischemia, but did not alter ischemia-induced changes in the autophagy marker proteins LC3II and p62. This is the 1st demonstration that the dPKC-dF1Fo interaction inhibitor has ATP- and infarct-sparing actions in vivo which may be associated with diminished opening of the mitochondrial permeability transition pore. These results support further development of this peptide as a first-in-class translational therapeutic for the treatment of cardiac IR injury.
Author Disclosures: M. Walker: None. R.W. Caldwell: None. J.A. Johnson: Research Grant; Significant; This research is currently supported by an AHA Greater Southeast Affiliate Grant-in-Aid #13GRNT17080109. Ownership Interest; Modest; A patent has been approved for the peptide discussed in the abstract. No financial relationships exist at present but they could be pursued..
This research has received full or partial funding support from the American Heart Association.
- © 2014 by American Heart Association, Inc.