Sevoflurane postconditioning is not mediated by ferritin accumulation and cannot be rescued by simvastatin in isolated streptozotocin-induced diabetic rat hearts.

Sevoflurane postconditioning (sevo postC) is an attractive and amenable approach that can protect the myocardium against ischemia/reperfusion (I/R)-injury. Unlike ischemic preconditioning (IPC), sevo postC does not require additional induced ischemic periods to a heart that is already at risk. IPC was previously shown to generate myocardial protection against I/R-injury through regulation of iron homeostasis and de novo ferritin synthesis, a process found to be impaired in the diabetic state. The current study investigated whether alterations in iron homeostasis and ferritin mRNA and protein accumulation are also involved in the cardioprotective effects generated by sevo postC. It was also investigated whether the protective effects of sevo postC in the diabetic state can be salvaged by simvastatin, through inducing nitric oxide (NO) bioavailability/activity, in isolated streptozotocin (STZ)-induced diabetic hearts (DH). Isolated rat hearts from healthy Controls and diabetic animals were retrogradely perfused using the Langendorff configuration and subjected to prolonged ischemia and reperfusion, with and without (2.4 and 3.6%) sevo postC and/or pre-treatment with simvastatin (0.5 mg/kg). Sevo postC significantly reduced infarct size and improved myocardial function in healthy Controls but not in isolated DH. The sevo postC mediated myocardial protection against I/R-injury was not associated with de novo ferrtin synthesis. Furthermore, simvastatin aggravated myocardial injury after sevo postC in STZ-induced DHs, likely due to increasing NO levels. Despite the known mechanistic overlaps between PC and postC stimuli, distinct differences underlie the cardioprotective interventions against myocardial I/R-injury and are impaired in the DH. Sevo postC mediated cardioprotection, unlike IPC, does not involve de novo ferritin accumulation and cannot be rescued by simvastatin in STZ-induced DHs

Protection by Nitric Oxide Donors of Isolated Rat Hearts Is Associated with Activation of Redox Metabolism and Ferritin Accumulation.

Preconditioning (PC) procedures (ischemic or pharmacological) are powerful procedures used for attaining protection against prolonged ischemia and reperfusion (I/R) injury, in a variety of organs, including the heart. The detailed molecular mechanisms underlying the protection by PC are however, complex and only partially understood. Recently, an 'iron-based mechanism' (IBM), that includes de novo ferritin synthesis and accumulation, was proposed to explain the specific steps in cardioprotection generated by IPC. The current study investigated whether nitric oxide (NO), generated by exogenous NO-donors, could play a role in the observed IBM of cardioprotection by IPC. Therefore, three distinct NO-donors were investigated at different concentrations (1-10 μM): sodium nitroprusside (SNP), 3-morpholinosydnonimine (SIN-1) and S-nitroso-N-acetylpenicillamine (SNAP). Isolated rat hearts were retrogradely perfused using the Langendorff configuration and subjected to prolonged ischemia and reperfusion with or without pretreatment by NO-donors. Hemodynamic parameters, infarct sizes and proteins of the methionine-centered redox cycle (MCRC) were analyzed, as well as cytosolic aconitase (CA) activity and ferritin protein levels. All NO-donors had significant effects on proteins involved in the MCRC system. Nonetheless, pretreatment with 10 μM SNAP was found to evoke the strongest effects on Msr activity, thioredoxin and thioredoxin reductase protein levels. These effects were accompanied with a significant reduction in infarct size, increased CA activity, and ferritin accumulation. Conversely, pretreatment with 2 μM SIN-1 increased infarct size and was associated with slightly lower ferritin protein levels. In conclusion, the abovementioned findings indicate that NO, depending on its bio-active redox form, can regulate iron metabolism and plays a role in the IBM of cardioprotection against reperfusion injury

Experimental protocols.

<p>Experimental protocols.</p

The Methionine-Centered Redox Cycle.

<p>The formation of methionine sulfoxide (MetO) can result from the oxidation of free methionine, or a methionyl residue of a protein. Additional oxidation will generate methionine sulfone (MetO₂), a product that is almost irreversible in biological systems, and can cause protein denaturation. MetO can be reduced by methionine sulfoxide reductases (MsrA or MsrB isoform), through thioredoxin (Trx). Thioredoxin reductase (TrxR) regenerates the oxidized Trx (Trx_ox) via critical components of the cellular redox system, NADP/NADP(H) [<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0159951#pone.0159951.ref032" target="_blank">32</a>].</p

Activity of cytosolic aconitase.

<p>Activity of cytosolic aconitase.</p

Infarct sizes of the rat hearts after exposure to the different experimental protocols.

<p>Data are presented as Mean ± SEM.* p < 0.05 versus I/R.</p

Activities of methionine sulfoxide reductase.

<p>Activities of methionine sulfoxide reductase.</p

Hemodynamic parameters of the rat hearts after exposure to the different experimental protocols.

<p>Hemodynamic parameters of the rat hearts after exposure to the different experimental protocols.</p

Ferritin and iron content at various times of the perfusion protocol.

<p>Ferritin and iron content at various times of the perfusion protocol.</p

Thioredoxin and thioredoxin-reductase protein levels.

<p>Thioredoxin and thioredoxin-reductase protein levels.</p