[MeArg1, NLe10]-apelin-12: Optimization of solid-phase synthesis and evaluation of biological properties in vitro and in vivo

Chemically modified peptide apelin-12 ([MeArg¹, NLe¹⁰]-apelin12, peptide M) is able to reduce reactive oxygen species (ROS) formation, cell death, and metabolic and ionic homeostasis disorders in experimental myocardial ischemia-reperfusion injury. These beneficial effects indicate the therapeutic potential of this compound in cardiovascular diseases. The goals of this work were to optimize the synthesis of peptide M, and to study its proteolytic stability and effect on the heart function of rabbits with doxorubicin (Dox) cardiomyopathy. We have developed a rational method of solid-phase synthesis of peptide M using the Fmoc methodology in combination with the temporary protection of the guanidine function of arginine residues by protonation (salt formation) during the formation of the amide bond. It avoids the formation of by-products, and simplifies the post-synthetic procedures, providing an increase in the yield of the final product of higher purity. Comparative evaluation of the proteolytic stability of peptide M and apelin-12 in human blood plasma was carried out using ¹H NMR spectroscopy. It was shown that the half-life of peptide M in plasma is approximately three times longer than that of apelin-12. Intravenous infusion of increasing doses of peptide M caused a gradual increase in left ventricular (LV) fractional shortening and ejection fraction in rabbits after 8 weeks of Dox administration (2 mg/kg weekly). The effect of the modified peptide on LV systolic dysfunction was significantly more pronounced than the effect of apelin-12, which suggests the promise of using this pharmacological agonist of the APJ receptor in patients with heart failure.

Galanin receptors activation modulates myocardial metabolic and antioxidant responses to ischaemia/reperfusion stress

The mechanisms of protective action of the neuropeptide galanin and its N-terminal fragments against myocardial ischaemia/reperfusion (I/R) injury remain obscure. The aim of this work was to study effects of a novel peptide agonist of galanin receptors [βAla14, His15]-galanin (2-15) (G1) and the full-length galanin (G2) on energy and antioxidant status of the heart with acute infarction. The peptides were synthesized by the automatic solid phase method using Fmoc technology. Their structure was identified by ¹ H-NMR spectroscopy and MALDI-TOF mass spectrometry. Experiments were performed on anaesthetized open-chest rats subjected to myocardial regional ischaemia and reperfusion. Intravenous (iv) administration of optimal doses of peptides G1 and G2 (1.0 and 0.5 mg/kg, respectively, at the onset of reperfusion significantly reduced infarct size (on average by 40% compared with control) and the plasma activity of creatine kinase-MB (CK-MB) and lactate dehydrogenase (LDH). These effects were associated with augmented preservation of aerobic energy metabolism, increased activity of Cu,Zn superoxide dismutase (Cu,Zn-SOD), catalase (CAT) and glutathione peroxidase (GSH-Px) and decreased lipid peroxidation in the area at risk (AAR) at the end of reperfusion. Peptide G1 showed more efficient recovery of the majority of metabolic and antioxidant parameters. The results provide evidence that the galaninergic system can be considered a promising target to reduce energy dysregulation and oxidative damage in myocardial I/R injury.

Galanin and its N-terminal fragments reduce acute myocardial infarction in rats

Agonists and antagonists for galanin receptor subtypes GalR1-3 can be used as putative therapeutics targets for the treatment of various human diseases. However, effects of galanin and its N-terminal fragments on myocardial ischemia/reperfusion injury remain unclear. This study was designed to assess the ability of the full-length galanin (GWTLNSAGYLLGPHAIDNHRSFSDKHGLT-NH2, G1), the natural fragments WTLNSAGYLL-NH2 (G2) and WTLNSAGYLLGPHA (G3), and their modified analogs WTLNAAGYLL (G4) and WTLNSAGYLLGPβAH (G5) to limit acute myocardial infarction in rats in vivo. The peptides G2-5 were synthesized by the automatic solid phase method using Fmoc technology, purified by preparative HPLC and identified by 1H NMR spectroscopy and MALDI -TOF mass spectrometry. The peptides G1-5 were administered by i.v. bolus injection at the onset of reperfusion at doses of 0.25, 0.50, 1.0, 2.0 or 3.0 mg/kg. The optimal doses of the peptides G1-5 significantly reduced the infarction area and decreased the activity of CK-MB and LDH in blood plasma at the end of reperfusion compared with the control. Among the peptides studied, G5 showed high efficacy in reducing the infarct size and the activity of necrosis markers in blood plasma with no significant effect on hemodynamic parameters. The results suggest that a novel agonist for galanin receptors G5 may be a promising tool for the treatment of myocardial ischemia/reperfusion (I/R) injury. Further studies are warranted to explore the stability of this peptide in blood plasma and mechanisms that contribute to its cardioprotective effects.