CENTRO DE INVESTIGACIONES CARDIOVASCULARES "DR. HORACIO EUGENIO CINGOLANI"
Unidad Ejecutora - UE
congresos y reuniones científicas
Nitric oxide and CaMKII: critical steps in the inotropic response to IGF-1
YEVES AM; VILA PETROFF M; BURGOS, JI; ENNIS IL
Ciudad Autónoma de Buenos Aires
Congreso; International Society for Heart Research XXII World Congress (ISHR).; 2016
International Society for Heart Research
Nitric oxide and CaMKII: critical steps in theinotropic response to IGF-1 Cardiacadaptation to aerobic exercise training includes improved cardiomyocytecontractility, by a non-yet clarified mechanism in which nitric oxide (NO) andCaMKII have been implicated. At the cellular level, IGF-1 is the main mediatorof the adaptive response to exercise. Ourpurpose was to explore the effect of IGF-1 on mice cardiomyocyte contractilityand the underlying signaling pathway. IGF-1(10nmol/L) increased cardiomyocyte shortening (128.12±4.62%, n=8 vsbasal; p˂0.05), effect abrogated by inhibition of NO production with thenon-selective nitric oxide synthase inhibitor L-NAME (2.5 mmol/L; 103.2±3.02%, n=5) or nitroguanidine (NG, 240 nmol/L), specific inhibitor forthe neuronal isoform (nNOS, 97.4±1.21%, n=5) and by CaMKII inhibitionwith KN93 (101.50±2.04%, n=6). In agreement, a significant increase in NO productionin response to IGF-1 (133.75±2.17%, n=16) was detected by epifluorescence withDAF-FM. Again, this was prevented byL-NAME (110.36±3.20%, n=11) and NG (114.44±1.83%, n=9), confirming theinvolvement of nNOS but not altered by KN93 (135.22±1.36%, n=9) suggesting thatCaMKII activation was downstream NO production. We explored the pathwayinvolved in nNOS activation by measuring AKT phosphorylation. As expected,IGF-1 increased P-AKT (185.90±10.18%, n=3; p˂0.05). SinceNO-dependent CaMKII activation has been proposed, we next determined CaMKII activity(P-CaMKII) and the phosphorylation of its downstream target Thr17-phospholamban,detecting a significant increase in both in the presence of IGF-1 (227.19±29.43%and 143.34±5.44%, n=3 respectively) but not when NO production was prevented byNG (126.61±5.48 and 65.76±15.04, n=3 respectively). Interestingly, similarresults showing nNOS and CaMKII activation were obtained in the hypertrophiedmyocardium of mice subjected to swimming training. Inconclusion, our results support a critical role of CaMKII in the positive inotropiceffect of IGF-1. Our findings suggest that IGF-1 through the IGF-1R triggers thephosphorylation of AKT which in turn activates nNOS and increases NO productionwhich would be responsible for CaMKII activation.