The antiarrhythmic effect and clinical consequences of ischemic preconditioning

Cardioprotection of ischemic preconditioning in rats involves upregulating adiponectin

It has been reported that ischemic preconditioning (IPC) and adiponectin (APN) are cardioprotective in many cardiovascular disorders. However, whether APN mediates the effect of IPC on myocardial injury has not been elucidated. This study was conducted to investigate whether IPC affects myocardial ischemic injury by increasing APN expression. Male adult rats with cardiac knockdowns of APN and its receptors via intramyocardial small-interfering RNA injection were subjected to IPC and then myocardial infarction (MI) at 24 h after IPC. Globular APN (gAd) was injected at 10 min before MI. APN mRNA and protein levels in myocardium as well as the plasma APN concentration were markedly high at 6 and 12 h after IPC. IPC ameliorated myocardial injury as evidenced by improved cardiac functions and a reduced infarct size. Compared with the control MI group, rats in the IPC + MI group had elevated levels of left ventricular ejection fraction and fractional shortening and a smaller MI size (P < 0.05). However, the aforementioned protective effects were ameliorated in the absence of APN and APN receptors, followed by the inhibition of AMP-activated protein kinase (AMPK) phosphorylation, but reversed by gAd treatment in wild-type rats, and AMPK phosphorylation increased (P < 0.05). Overall, our results suggest that the cardioprotective effects of IPC are partially due to upregulation of APN and provide a further insight into IPC-mediated signaling effects.

Remote Liver Ischemic Preconditioning Protects against Sudden Cardiac Death via an ERK/GSK-3β-Dependent Mechanism

BACKGROUND

Preconditioning stimuli conducted in remote organs can protect the heart against subsequent ischemic injury, but effects on arrhythmogenesis and sudden cardiac death (SCD) are unclear. Here, we investigated the effect of remote liver ischemia preconditioning (RLIPC) on ischemia/reperfusion (I/R)-induced cardiac arrhythmia and sudden cardiac death (SCD) in vivo, and determined the potential role of ERK/GSK-3βsignaling.

METHODS/RESULTS

Male Sprague Dawley rats were randomized to sham-operated, control, or RLIPC groups. RLIPC was induced by alternating four 5-minute cycles of liver ischemia with 5-minute intermittent reperfusions. To investigate I/R-induced arrhythmogenesis, hearts in each group were subsequently subjected to 5-minute left main coronary artery ligation followed by 20-minute reperfusion. RLIPC reduced post-I/R ventricular arrhythmias, and decreased the incidence of SCD >threefold. RLIPC increased phosphorylation of cardiac ERK1/2, and GSK-3β Ser9 but not Tyr216 post-I/R injury. Inhibition of either GSK-3β (with SB216763) or ERK1/2 (with U0126) abolished RLIPC-induced antiarrhythmic activity and GSK-3β Ser9 and ERK1/2 phosphorylation, leaving GSK-3β Tyr216 phosphorylation unchanged.

CONCLUSIONS

RLIPC exerts a powerful antiarrhythmic effect and reduces predisposition to post-IR SCD. The underlying mechanism of RLIPC cardioprotection against I/R-induced early arrhythmogenesis may involve ERK1/2/GSK-3β Ser9-dependent pathways.

Comparison of cardioprotective and anti-inflammatory effects of ischemia pre- and postconditioning in rats with myocardial ischemia-reperfusion injury

OBJECTIVE

To compare cardioprotective and anti-inflammatory effects of ischemia preconditioning (IPC) and ischemia postconditioning (IPOC) in a rat myocardial ischemia-reperfusion injury (IRI) model.

METHODS

Forty Sprague-Dawley rats were randomly divided equally into four groups. In the groups other than the sham group, the left anterior descending coronary artery was ligated for 30 min followed by a 180 min reperfusion in vivo. The control group was subjected to no additional intervention, the IPC group to three cycles of 5 min ischemia separated by 5 min reperfusion before the index ischemia and the IPOC group to three cycles of 10 s ischemia separated by 10 s reperfusion immediately after the end of the index ischemia. Hemodynamic changes during the ischemia and reperfusion were recorded. At 180 min of reperfusion, serum concentrations of troponin I (TnI), tumor necrosis factor α (TNF-α) and high-mobility group box 1 (HMGB-1) were assayed, and the infarction size was assessed by Evans blue and triphenyltetrazolium chloride staining.

RESULTS

Compared to the control group, infarct size and serum concentrations of TnI, TNF-α and HMGB1 at 180 min of reperfusion were significantly reduced in the IPC and IPOC groups. However, infarct size and serum concentrations of TNF-α and HMGB1 at 180 min of reperfusion were significantly increased in the IPOC group compared to the IPC group.

CONCLUSIONS

In the rats with myocardial IRI in vivo, both IPC and IPOC can produce significant cardioprotective and anti-inflammatory effects. However, cardioprotective and anti-inflammatory effects provided by IPOC are weaker than with IPC.

Periodic acceleration (pGz) prior to whole body ischemia reperfusion injury provides early cardioprotective preconditioning

AIMS

Periodic acceleration (pGz) is a method that applies repetitive sinusoidal head-to-foot motion to the horizontally positioned body. pGz adds pulses to the circulation as a function of frequency, thereby increasing shear stress to the endothelium. Pulsatile shear stress increases release of cardioprotective endothelial-derived nitric oxide prostaglandin E-2 and prostacyclin into the circulation. We investigated whether pGz may be effective as an early preconditioning strategy when applied one hour prior to whole body ischemia reperfusion injury induced by ventricular fibrillation (VF).

MAIN METHODS

Twenty anesthetized and paralyzed male swine were randomized to one hour of pGz and conventional mechanical ventilation [PC] or solely conventional mechanical ventilation [Control] prior to VF and resuscitation. After eight minutes of unsupported VF, cardiopulmonary resuscitation was carried out followed by defibrillation. Hemodynamics, electrocardiogram, echocardiogram, regional blood flows, and markers of global myocardial injury were measured. Protein expression of endothelial-derived nitric oxide synthase (eNOS), phosphorylated eNOS (p-eNOS), serine/threonine kinase Akt total (t-Akt), and phosphorylated (p-Akt) were determined by immunoblotting.

KEY FINDINGS

All animals had spontaneous return of circulation after cardiopulmonary resuscitation (CPR) and defibrillation. Preconditioned animals had less hemodynamically significant arrhythmias, less myocardial stunning, and greater regional blood flows to the brain, heart, kidneys, and ileum than Controls. Troponin I and creatine phosphokinase values in PC were 65% of the values present in Controls. In addition, preconditioned animals had higher protein expression of cardiac eNOS, p-eNOS, t-Akt, and p-Akt than Controls.

SIGNIFICANCE

pGz preconditioning confers early cardioprotection in a model of whole body ischemia reperfusion injury.

Inhibition of the Na+/H+ exchanger protects the immature rabbit myocardium from ischemia and reperfusion injury

BACKGROUND

This study investigated the cardioprotective effects of pharmacologic pretreatment with HOE642, a selective Na(+)/H(+ )exchanger (NHE) isoform-1 inhibitor, in immature rabbit hearts, as compared with ischemic preconditioning (IPC).

METHODS

For this study, 36 isolated immature New Zealand white rabbit hearts were equilibrated on the Langendorff apparatus. They were randomly divided into three groups: control group, IPC group, and HOE642 group. The hearts in each group were subjected to 60 min of ischemia plus 60 min of reperfusion (I/R). In the IPC group, the hearts were preconditioned by 5 min of ischemia followed by 10 min of reperfusion before I/R. In the HOE642 group, the hearts were pretreated with HOE642 (5 mumol/l) for 15 min before I/R. Left ventricular performance (LVDP, +dp/dt(max), -dp/dt(max)), coronory artery flow (CF), myocardial water content, adenosine triphosphate (ATP), cardiac-specific enzymes (creatine kinase [CK], CK fraction MB [CK-MB], and lacate dehydrogenase [LDH]), and intracellular calcium content were measured. Myocardial ultrastructure was observed under transmission electron microscopy.

RESULTS

The recovery rates for left ventricular performance and CF in both the HOE642 and the IPC groups increased compared with those for the control subjects (p < 0.05). Moreover, the recovery rates for LVDP, +dp/dt(max), -dp/dt(max), and CF in the HOE642 group were markedly higher than in the IPC group at most time points of reperfusion (p < 0.05). Compared with the control group, CK, CK-MB, and LDH in the HOE642 group were decreased significantly (p < 0.05), whereas only LDH was reduced in the IPC group (p < 0.05). Water content was significantly reduced and ATP reserve was significantly increased in both the IPC and HOE642 groups (p < 0.05). However, compared with the IPC group, water content in the HOE642 group was significantly lower (81.26% +/- 1.26% vs 83.58% +/- 1.27%; p < 0.05) and ATP was significantly higher (21.46 +/- 2.40 vs 17.66 +/- 1.50 mug/g; p < 0.05). The HOE642 pretreatment exerted a better effect of reducing calcium overload than IPC (265.8 +/- 41.1 vs 408.5 +/- 56.8 mg/kg dry weight; p < 0.05). The blinded ultrastructural assessment under transmission electron microscopy showed that HOE642 brought about more myocyte salvage than IPC.

CONCLUSION

This study demonstrated that HOE642 pretreatment is superior to IPC against ischemia and reperfusion injury in isolated immature rabbit myocardium.