Previously, we demonstrated protection against hypoxic injury in neonatal cardiac myocytes and reduced release of cardiac
troponin I from perfused rat hearts by a novel
peptide inhibitor [NH2-YGRKKRRQRRRMLATRALSLIGKRAISTSVCAGRKLALKTIDWVSFDYKDDDDK-] of the
delta protein kinase C (δPKC) interaction with the "d" subunit of mitochondrial F1Fo
ATP synthase (dF1Fo). This
peptide was developed in our laboratory and contains: an
HIV-Tat protein transduction domain; a mitochondrial targeting motif; the δPKC-dF1Fo inhibitor sequence; and a FLAG
epitope. In the present study the δPKC-dF1Fo inhibitor attenuated co-immunoprecipitation of δPKC with dF1Fo, improved recovery of contractility, diminished levels of tissue t-carbonyls and
4-hydroxy-2-nonenal (HNE), and reduced
2,3,5-triphenyltetrazolium chloride-monitored
infarct size following simulated global
ischemia/reperfusion (IR) exposures. Perfusion of hearts with this
peptide prior to IR enhanced
ATP levels 2.1-fold, improved
ADP (state 3)- and
FCCP (maximal)-stimulated respiration in mitochondrial oxygen consumption assays, and attenuated Ca(++)-induced mitochondrial swelling following ischemic injury. Mitochondrial membrane potential (assessed by JC-1) was also improved 1.6-fold by the inhibitor in hearts subsequently exposed to IR injury. Brief IR exposures did not cause mitochondrial loss of
cytochrome c in the presence or absence of the inhibitor. Additionally, the inhibitor did not modify accumulation of the autophagy marker LC3II after brief IR injury. Our results support the potential for this first-in-class
peptide as a translational agent for combating cardiac IR injury.