Isoflurane Postconditioning Protects against Reperfusion Injury by Preventing Mitochondrial Permeability Transition by an Endothelial Nitric Oxide Synthase–dependent Mechanism

Abstract

Background The role of endothelial nitric oxide synthase (eNOS) in isoflurane postconditioning (IsoPC)-elicited cardioprotection is poorly understood. We addressed this issue using eNOS-/- mice. Methods In vivo or Langendorff-perfused mouse hearts underwent 30 min of ischemia followed by 2 h of reperfusion in the presence and absence of postconditioning produced with isoflurane 5 min before ischemia and 3 min after reperfusion. Ca2+-induced mitochondrial permeability transition pore opening was assessed in isolated mitochondria. Echocardiography was used to evaluate ventricular function. Results Postconditioning with 0.5, 1.0, and 1.5 minimum alveolar concentrations of isoflurane decreased infarct size from 56 ± 10% (n = 10) in control to 48 ± 10%, 41 ± 8% (n = 8, P < 0.05), and 38 ± 10% (n = 8, P < 0.05), respectively and improved cardiac function in wild-type mice. Improvement in cardiac function by IsoPC was blocked by NG-nitro-L-arginine methyl ester (a nonselective NOS inhibitor) administered either prior to ischemia or at the onset of reperfusion. Mitochondria isolated from postconditioned hearts required significantly higher in vitro Ca2+ loading than control (78 ± 29 vs. 40 ± 25 μM CaCl2 mg protein-1, n = 10, P < 0.05) to open the mitochondrial permeability transition pore. Hearts from eNOS-/- mice displayed no marked differences in infarct size, cardiac function, and sensitivity of mitochondrial permeability transition pore to Ca2+, compared to the wild-type hearts. However, IsoPC failed to alter infarct size, cardiac function or the amount of Ca2+ necessary to open the mitochondrial permeability transition pore in mitochondria isolated from the eNOS-/- hearts compared to control hearts. Conclusions IsoPC protects mouse hearts from reperfusion injury by preventing MPT pore opening in an eNOS-dependent manner. Nitric oxide functions as both a trigger and a mediator of cardioprotection produced by IsoPC.

Decreased tetrahydrobiopterin and disrupted association of Hsp90 with eNOS by hyperglycemia impair myocardial ischemic preconditioning

“…Mice were anesthetized with pentobarbital sodium (100 mg/kg ip) and ventilated with room air supplemented with 100% oxygen at a rate of ϳ104 breaths/min with a tidal volume of ϳ225 l using a mouse ventilator (Hugo Sachs Elektronic, Hugsteten, Germany), as previously described (5,(22)(23)(24)(25). The heart was exposed via a thoracotomy at the fourth intercostal space.…”

The role of gasotransmitters NO, H2S and CO in myocardial ischaemia/reperfusion injury and cardioprotection by preconditioning, postconditioning and remote conditioning

“…Mitochondria isolated from postconditioned hearts require significantly higher in vitro calcium loading than did controls to open the mPTP. In hearts from eNOS knockout mice, isoflurane PostC failed to alter the infarct size or mPTP opening (Ge et al, 2010). The mechanism(s) involved in modifying mPTP opening might involve indirect effects through protein kinases or direct SNO-protein modifications.…”

The Effect of Mitochondrial Complex I-Linked Respiration by Isoflurane Is Independent of Mitochondrial Nitric Oxide Production

“…For example, it may act as a trigger and mediator of isoflurane-induced delayed preconditioning in rabbit myocardium [12]. Furthermore, isoflurane potentiates ischemic postconditioning via an NO-dependent mechanism [13]. It has been suggested that mitochondria contain NO synthase (NOS) and produce NO to regulate respiration [14].…”