Protective Effects of Cyclo(L-Leu-L-Tyr) against Postischemic Myocardial Dysfunction in Guinea-Pig Hearts

• Published in: Biological & Pharmaceutical Bulletin Vol. 34; no. 3; pp. 335 - 342
• Main Authors: Mitsui-Saitoh, Kumiko, Furukawa, Tadashi, Akutagawa, Takashi, Hasada, Keiko, Mizutani, Hideki, Sugimoto, Yumi, Yamada, Jun, Niwa, Masatake, Hotta, Yoshihiro, Takaya, Yoshiaki
• Format: Journal Article
• Language: English
• Published: Japan The Pharmaceutical Society of Japan 2011; Pharmaceutical Society of Japan; Japan Science and Technology Agency
• Subjects: 31P-NMR; Adenosine Triphosphate - metabolism; Animals; Antioxidants - pharmacology; Antioxidants - therapeutic use; apoptosis; Apoptosis - drug effects; Calcium - metabolism; Cardiovascular Agents - pharmacology; Cardiovascular Agents - therapeutic use; Caspase 3 - metabolism; cyclic dipeptide; Cyclosporine - pharmacology; Dipeptides - pharmacology; Dipeptides - therapeutic use; electron paramagnetic resonance; Female; Guinea Pigs; ischemia-reperfusion injury; Male; Mitochondria - metabolism; Mitochondrial Membrane Transport Proteins - antagonists & inhibitors; mitochondrial permeability transition pore; Myocardial Ischemia - drug therapy; Myocardial Ischemia - metabolism; Myocardial Ischemia - pathology; Myocardial Reperfusion Injury - metabolism; Myocardial Reperfusion Injury - pathology; Myocardial Reperfusion Injury - prevention & control; Myocardium - metabolism; Myocardium - pathology; Peptides, Cyclic - chemistry; Peptides, Cyclic - pharmacology; Peptides, Cyclic - therapeutic use; Structure-Activity Relationship; Ventricular Dysfunction, Left - drug therapy; Ventricular Dysfunction, Left - metabolism
• ISSN: 0918-6158; 1347-5215
• DOI: 10.1248/bpb.34.335

The protective effects of cyclic dipeptides in alcoholic beverages were investigated in the perfused guinea-pig hearts subjected to ischemia and reperfusion. Subsequently, in order to determine the importance of cyclic dipeptide structure, the effects of cyclo(L-Leu-L-Tyr) (cLY) were compared with those of the newly synthesized non-cyclic dipeptides, L-Leu-L-Tyr (LY) and L-Tyr-L-Leu (YL). After reperfusion, pressure recovery (%) in the left ventricle reached a peak of over 90% in the presence of cLY (10−6 M and 10−5 M) (control: 22.9%). The recovery by LY and YL was significantly lower than that by cLY, and ATP levels simultaneously monitored using 31P-NMR were already lower during the ischemic end period than those observed with cLY treatment. In perfused mitochondrial preparations, cLY significantly inhibited mitochondrial Ca2+ ([Ca2+]m) elevation in a similar way to that of the mitochondrial permeability transition pore (MPTP) inhibitor cyclosporin A. In vitro electron paramagnetic resonance (EPR) revealed that the active oxygen radicals quenching activity of cLY was greater than those of non-cyclic dipeptides. cLY inhibited caspase-3-induced apoptosis. The cyclic dipeptide structure inhibits opening of the MPTP by preventing [Ca2+]m overload-induced apoptosis related to mitochondrial active oxygen radical accumulation in ischemia-reperfusion hearts.