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Myocardial impact and cardioprotective effects of apelin-13 and a c-terminal-modified analog during lps and clp experimental sepsis
Intensive Care Medicine Experimental volume 3, Article number: A436 (2015)
Apelin-13 (APL-13) is a member of an endogenous peptide's family (APLs) with powerful inotropic and cardioprotective properties. APLs bind to the dedicated receptor APJ-R, a member of the G protein-coupled receptor superfamily, all being widely expressed in the cardiovascular system. We have already shown that APL-13 infusion, was protective against LPS-induced myocardial dysfunction and death vs. dobutamine . Furthermore, we have shown that, C-terminal Phe(13) modification of APL-13 by unnatural amino acids can change ligand binding and APJ-R signaling .
Understanding the beneficial impact of APL-13 on LPS-induced myocardial injury vs. dobutamine, and assessing functional and biological effects of a new selected linear APL-13 analog with enhanced affinity, and their impact in the context of sepsis.
Myocardial dysfunction was induced by intra-peritoneal injection of LPS (E. Coli 055:B5, 10 mg/kg) or Cecal Ligature and Puncture (CLP) in male Sprague-Dawley rats. Myocardial injury was biologically evaluated by analyzing of different cellular pathway of apoptosis and inflammation by Western blot. Myocardial function was assessed ex-vivo by Langendorff and in vivo by echocardiography by comparing APL-13 to Tyr(Obn). Tyr(OBn)(13) substitution led to a 60-fold increase in binding affinity vs. APL-13 .
LPS-challenged rats treated with APL-13 exhibited a clear reduction of both apoptosis (cleaved caspase-3, BAX/BCL-2 ratio) and inflammation (iNOS and MIF) markers, with significant alterations in the Akt/GSK3b/mTor and P38/Erk pathways underscoring the cardioprotective effect of APLs. Organic Langendorff assays confirmed cellular data  in that enhanced affinity confers to Tyr(Obn) analog a more effective and potent inotropic activity than APL-13, as shown by the increased left ventricular developed pressure (LVDP) (% baseline, 1pM : APL-13, 8 ± 13 vs. Tyr(Obn), 60 ± 15 ; p < 0.05), (30pM : APL-13, 124 ± 25 vs. Tyr(Obn), 372 ± 106 ; p < 0.05). APLs sensibility was increased in 8h CLP-challenged hearts, as it was in 24h LPS-challenged hearts , suggesting upregulation of the myocardial apelinergic pathway during polymicrobial sepsis. Indeed, CLP model of sepsis was characterized at 8h by a reduced cardiac output (Sham, 170 ± 3 vs. CLP, 99 ± 5 ml/min, p < 0.05) with an increased parietal thickness (Sham, 0.15 ± 0.002 vs. CLP, 0.23 ± 0.003 cm, p < 0.05) in vivo.
APLs are new safer supporting drugs in sepsis. Chemical modifications can optimize the inotropic potency of APLs opening a novel field of therapeutic opportunities. Ongoing works are to evaluate the functional effect of these new analogs in vivo, with Pressure-Volume curve device, and to further test their comparative cardioprotective potential during experimental CLP sepsis.
Lesur O, Chagnon F, Murza A, Sarret P, Marsault E, Salvail D: Apelin is cardioprotective and life-saving over dobutamine in a murine model of endotoxin-induced myocardial dysfunction. Intensive Care Med Exp. 2014, 2 (Suppl 1): P11-10.1186/2197-425X-2-S1-P11. 0100
Murza A, Besserer-Offroy É, Côté J, Bérubé P, Longpré JM, Dumaine R, et al: C-Terminal modifications of apelin-13 significantly change ligand binding, receptor signaling, and hypotensive action. J Med Chem. 2015, 58 (5): 2431-2440. 10.1021/jm501916k.