Insulin inhibits leukocyte-endothelium adherence via an Akt-NO-dependent mechanism in myocardial ischemia/reperfusion.
Clinical evidence indicates that intensive insulin therapy during critical illness protects the endothelium and contributes to prevention of organ failure and death but the mechanisms involved remain unclear. This study was designed to test the hypothesis that insulin inhibits adherence of polymorphonuclear leukocytes (PMNs) to endothelial cells in myocardial ischemia/reperfusion (MI/R) and to investigate the underlying mechanisms. Anesthetized rabbits were subjected to MI/R (45 min/4 h) and randomly received saline, glucose-insulin-potassium (GIK) or GK respectively (2 mL/kg/h, i.v.). In vitro study was performed on cultured endothelial cells subjected to simulated ischemia/reperfusion. In vivo treatment with GIK but not GK attenuated myocardial injury as evidenced by reduced plasma creatine kinase activity, myocardial apoptosis and infarct size in MI/R rabbits compared with the saline group. Interestingly, GIK but not GK significantly decreased coronary endothelial expression of P-selectin and intercellular adhesion molecule-1 (ICAM-1), inhibited adherence of PMNs to coronary endothelium (107.7+/-7.4 vs. 155.0+/-9.2 PMNs/mm(2) in saline group, n=8, P<0.01), and therefore decreased myocardial PMNs accumulation. In cultured endothelial cells subjected to simulated ischemia/reperfusion, insulin (10(-)(7) M) increased Akt activity and eNOS phosphorylation with subsequent NO production, and concurrently exerted an anti-adhesive effect as manifested by reduced endothelial P-selectin and ICAM-1 surface expression and PMNs adherence (13.7+/-1.3% vs. 22.2+/-1.9% in vehicle, n=9, P<0.01), all of which are abolished by the specific Akt inhibitor. Furthermore, inhibition of insulin-stimulated NO production using either the selective eNOS inhibitor cavtratin or the NOS inhibitor L-NAME blocked the anti-adhesive effect of insulin. These results demonstrate that insulin reduces endothelial P-selectin and ICAM-1 expression, and thus inhibits leukocyte-endothelium adherence in MI/R rabbit hearts. The anti-adhesive property by insulin may be mediated by the Akt-mediated and NO-dependent pathway.
Li
Jia
J
Department of Physiology and Cardiology, Xijing Hospital, Fourth Military Medical University, Xi'an 710032, China.
Wu
Feng
F
Zhang
Haifeng
H
Fu
Feng
F
Ji
Lele
L
Dong
Ling
L
Li
Qiuxia
Q
Liu
Wenchong
W
Zhang
Yuan
Y
Lv
Anlin
A
Wang
Haichang
H
Ren
Jun
J
Gao
Feng
F
D000818:Animals; D001786:Blood Glucose / Q000378:metabolism; D002448:Cell Adhesion / Q000187:drug effects; D002462:Cell Membrane / Q000187:drug effects / Q000378:metabolism; D042783:Endothelial Cells / Q000166:cytology* / Q000187:drug effects / Q000201:enzymology; D004789:Enzyme Activation; D038362:Glycogen Synthase Kinase 3 / Q000378:metabolism; D000071679:Glycogen Synthase Kinase 3 beta; D006801:Humans; D007328:Insulin / Q000494:pharmacology*; D018799:Intercellular Adhesion Molecule-1 / Q000378:metabolism; D015428:Myocardial Reperfusion Injury / Q000201:enzymology* / Q000473:pathology*; D009504:Neutrophils / Q000166:cytology* / Q000187:drug effects / Q000201:enzymology; D009569:Nitric Oxide / Q000378:metabolism*; D052250:Nitric Oxide Synthase Type III / Q000378:metabolism; D019007:P-Selectin / Q000378:metabolism; D010766:Phosphorylation / Q000187:drug effects; D051057:Proto-Oncogene Proteins c-akt / Q000378:metabolism*; D011817:Rabbits
D001786:Blood Glucose; D007328:Insulin; D019007:P-Selectin; D018799:Intercellular Adhesion Molecule-1; D009569:Nitric Oxide; D052250:Nitric Oxide Synthase Type III; D000071679:Glycogen Synthase Kinase 3 beta; D051057:Proto-Oncogene Proteins c-akt; D038362:Glycogen Synthase Kinase 3