Decreased myocardial injury and improved contractility after administration of a peptide derived against the alpha-interacting domain of the L-type calcium channel.
Bottom Line: Activation of the channel also alters mitochondrial function.In search of the mechanism for the effect, we found that intracellular calcium ([Ca(2+)]i, Fura-2), superoxide production (dihydroethidium fluorescence), mitochondrial membrane potential (Ψm, JC-1 fluorescence), reduced nicotinamide adenine dinucleotide production, and flavoprotein oxidation (autofluorescence) are decreased after application of AID-TAT peptide.Application of AID-TAT peptide significantly decreased infarct size and supported contractility up to 12 weeks postcoronary artery occlusion as a result of a decrease in metabolic demand during reperfusion.
Affiliation: School of Anatomy, Physiology and Human Biology, The University of Western Australia, Crawley, WA, Australia (H.M.V., L.C.H.).Show MeSH
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Mentions: Because AID‐TAT peptide slows the inactivation rate of ICa‐L current,19–20 we examined the effect of the peptide on changes in [Ca2+]i after activation of the channel. We and others have shown previously that application of H2O2 can directly increase ICa‐L current.4,10–11 As little as 5 minutes of exposure to 30 to 50 μmol/L of H2O2 can cause further release of superoxide from the mitochondria without inducing apoptosis or necrosis and is sufficient to increase protein synthesis, consistent with the development of myocyte hypertrophy.10,12 ROS‐induced ROS‐release is proposed to occur during reperfusion and can lead to mitochondrial permeability transition pore opening and arrhythmia.27–29 We mimicked the OS associated with reperfusion by applying 40 μmol/L of H2O2 to ventricular myocytes for 5 minutes, followed by 10 U/mL of CAT to degrade the H2O2. Consistent with previous studies,10 addition of H2O2 resulted in a small, but significant, increase in [Ca2+]i assessed as changes in Fura‐2 that could be attenuated with addition of the ICa‐L antagonist, nisoldipine (Figure 3A and 3B). Application of 1 μmol/L of AID‐TAT peptide had no effect on the increase in Fura‐2 signal induced by 40 μmol/L of H2O2. However, the addition of 10 μmol/L of AID‐TAT peptide attenuated the increase in Fura‐2 signal induced by H2O2 by ≈75% (Figure 3C and 3D). Application of AID‐TAT peptide did not alter basal Fura‐2 signal, indicating that the peptide did not prevent calcium influx through the alpha subunit of the channel (Figure 3D, inset right). These data suggest that 10 μmol/L, but not 1 μmol/L, of AID‐TAT peptide can alter ICa‐L‐activated calcium influx in myocytes.
Affiliation: School of Anatomy, Physiology and Human Biology, The University of Western Australia, Crawley, WA, Australia (H.M.V., L.C.H.).