IL-6 induces PI 3-kinase and nitric oxide-dependent protection and preserves mitochondrial function in cardiomyocytes.
OBJECTIVE
Interleukin-6 (IL-6) is a pro-inflammatory cytokine which is a prognostic marker associated with left ventricular contractile dysfunction and heart failure. On the other hand, IL-6 activates signalling pathways which mediate delayed ischemic preconditioning. We have therefore studied the cellular mechanisms of IL-6-induced cardioprotection.


METHODS
Inducible nitric oxide synthase (iNOS) expression, cardiomyocyte calcium handling, mitochondrial energetics, and the activation of protective signalling pathways in response to IL-6 were studied in a model of simulated ischemia/reperfusion (sI/R) in isolated neonatal rat ventricular cardiomyocytes.


RESULTS
Reperfusion after sI/R induced a rise in cytosolic [Ca2+], a loss of cell morphology and integrity, and a transient increase in mitochondrial potential (Deltapsi m), followed by mitochondrial swelling and collapse of Deltapsi m. Pre-treatment of cardiomyocytes with 10 ng/ml IL-6 for 6 h, 24 h prior to sI/R prevented the secondary rise in cytosolic [Ca2+] and induced expression of iNOS and NO-dependent protection against sI/R injury. The protection against sI/R was concomitant with a NO-dependent reduction in the amplitude of cytosolic Ca2+ transients. IL-6 induced an increase in inner mitochondrial membrane polarisation and increased mitochondrial Ca2+ loading (rhod-2 fluorescence) at baseline, but prevented the reperfusion-induced changes in mitochondrial function. IL-6 pre-treatment also resulted in activation of the phosphatidylinositol (PI) 3-kinase/Akt pathway, and both iNOS induction and IL-6-dependent protection were blocked by the PI 3-kinase inhibitor wortmannin.


CONCLUSIONS
IL-6 induces a PI 3-kinase and NO-dependent protection of cardiomyocytes, which is associated with alterations in mitochondrial Ca2+ handling, inhibition of reperfusion-induced mitochondrial depolarisation, swelling and loss of structural integrity, and suppression of cytosolic Ca2+ transients.
Smart
Nicola
N
Cardiovascular Division, King's College London School of Medicine, Department of Cardiology, The Rayne Institute, St Thomas' Hospital, Lambeth Palace Road, London SE1 7EH, UK.
Mojet
Mart H
MH
Latchman
David S
DS
Marber
Michael S
MS
Duchen
Michael R
MR
Heads
Richard J
RJ
D000730:Androstadienes / Q000494:pharmacology; D000818:Animals; D002118:Calcium / Q000378:metabolism; D002478:Cells, Cultured; D003600:Cytosol / Q000378:metabolism; D004791:Enzyme Inhibitors / Q000494:pharmacology; D015850:Interleukin-6 / Q000494:pharmacology*; D008564:Membrane Potentials / Q000187:drug effects; D018613:Microscopy, Confocal; D008929:Mitochondria, Heart / Q000378:metabolism*; D015428:Myocardial Reperfusion Injury / Q000378:metabolism / Q000473:pathology / Q000517:prevention & control*; D032383:Myocytes, Cardiac / Q000378:metabolism*; D009569:Nitric Oxide / Q000378:metabolism*; D052247:Nitric Oxide Synthase Type II / Q000378:metabolism; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism*; D000081082:Phosphoinositide-3 Kinase Inhibitors; D051381:Rats; D017207:Rats, Sprague-Dawley; D012519:Sarcoplasmic Reticulum / Q000378:metabolism; D000077191:Wortmannin
D000730:Androstadienes; D002118:Calcium; D004791:Enzyme Inhibitors; D015850:Interleukin-6; D009569:Nitric Oxide; D052247:Nitric Oxide Synthase Type II; D019869:Phosphatidylinositol 3-Kinases; D000081082:Phosphoinositide-3 Kinase Inhibitors; D000077191:Wortmannin