A Novel Water-Soluble and Cell-Permeable Calpain Inhibitor Protects Myocardial and Mitochondrial Function in Postischemic Reperfusion

Abstract

The effects of the novel calpain inhibitor A-705239 were studied in isolated perfused rabbit hearts subjected to 45 min of global ischemia, followed by 60 min of reperfusion. During 15 min of perfusion the inhibitor accumulated in myocardial tissue up to 16 times the concentration in the perfusate. Almost complete recovery and survival of heart function (90%) was seen with an inhibitor concentration of 10(-8) M in the perfusion fluid when the compound was administered prior to ischemia. Left ventricular pressure amplitude and coronary flow showed significantly higher values during reperfusion in the presence of the inhibitor. A-705239 significantly reduced the release of creatine kinase, from 166+/-49 U/l in untreated hearts to 44+/-10 U/l, and diminished the release of lactate dehydrogenase from 118+/-20 U/l in untreated hearts to 63+/-4 U/l. Mitochondrial dysfunction following ischemia and reperfusion was markedly attenuated by the inhibitor. Thus, the state 3 respiration rate only decreased to 4.2 in contrast to 2.6 nmol O2/(min x mg s.w.) in untreated hearts, reflecting a reduced damage of oxidative phosphorylation. Furthermore, in the presence of the inhibitor the inner mitochondrial membranes became less permeable as indicated by a smaller leak respiration. The excellent properties of A-705239 should make this compound a valuable tool for further pharmacological studies.

Reduction of myocardial infarction by calpain inhibitors A-705239 and A-705253 in isolated perfused rabbit hearts

“…No reduction in the release of lactate dehydrogenase and creatine kinase by calpain inhibition, as observed after global myocardial ischemia (Chen et al, 2002;Neuhof et al, 2003;Liu and Schellmann, 2003), was found in our study with transient local ischemia. This may be due to an enzyme loss from small affected tissue volumes with insufficient concentration for detection.…”

“…Besides direct myofilament disintegration, mitochondrial dysfunction is also considered to contribute essentially to cardiac dysfunction and myocyte injury during ischemia and reperfusion (Lesnefsky et al, 2001). This assumption is supported by observations that calpain inhibition (Neuhof et al, 2003) or the prevention of calpain activation by Na q /H q exchange inhibition (Chen et al, 2002) reduces mitochondrial dysfunction during myocardial ischemia and reperfusion.…”

“…The remarkably low inhibitor concentration of 10 -8 M used in these experiments, which was found to be the most effective in a recent study on global myocardial ischemia (Neuhof et al, 2003), is due to its excellent water solubility and good tissue availability which results in a 16-fold inhibitor accumulation in the heart muscle. Increased attention has been focused over the past two decades on calpains, besides cardiomyocyte contracture, reactive oxygen species and lysosomal proteases, as leading players in lethal myocardial cell injury during ischemia and reperfusion.…”

“…Calpain activity increases during myocardial hypoxia (Iizuka et al, 1991), and activated calpains were localized by specific antibodies in infarcted regions of the human heart . Calpain inhibition, on the other hand, attenuates or prevents myocardial tissue damage and mitochondrial dysfunction by ischemia and reperfusion (Neuhof et al, 2003). Increased calpain activity during hypoxia (Iizuka et al, 1991) can be reduced with peptidyl aldehyde calpain inhibitor-I.…”

Inhibition of Calpain Prevents N-Methyl-d-aspartate-Induced Degeneration of the Nucleus Basalis and Associated Behavioral Dysfunction

“…This finding is important in light of the fact that the proteasome complex contributes to a variety of neurodegenerative disorders (Rubinsztein, 2006;Pan et al, 2008). A-705253 has previously been shown to rapidly and effectively penetrate myocardial tissues, and it exerts its effects on cellular targets within minutes after perfusion (Neuhof et al, 2003(Neuhof et al, , 2004, making it an ideal compound for studying calpain in vivo.…”