Pathobiology and Clinical Impact of Reperfusion Injury

Pharmacokinetics and safety of a single dose of the novel necrosis inhibitor LC28-0126 in healthy male subjects

AIMS

A novel necrosis inhibitor, LC28-0126, is expected to have a cellular protective effect from ischaemic reperfusion injury in acute myocardial infarction. The objective of this study was to investigate the safety, tolerability and pharmacokinetics of LC28-0126 after a single intravenous administration in healthy male subjects.

METHODS

The study was a dose-block-randomized, double-blind, placebo-controlled, single ascending dose, first-in-human trial. Subjects were randomly assigned to receive 0.3, 1, 3, 10, 25, 50, 100 or 200 mg of LC28-0126. LC28-0126 was infused for 30 min and 5 min in cohorts 1 and 2, respectively. An interim analysis to assess the tolerability and pharmacokinetics was conducted in each dose group. Blood samples were taken to determine plasma LC28-0126 concentrations from predose to 48 or 144 h postdose, and urine samples were taken from predose to 48 or 72 h postdose.

RESULTS

Overall, 89 subjects were randomly assigned to the dose groups of the two cohorts. LC28-0126 was well tolerated, and no serious adverse events were reported. LC28-0126 showed rapid disposition in the distribution phase. Overall, the fraction of unchanged LC28-0126 excreted during the 48 or 72 h after administration was below 5%. The systemic exposure of LC28-0126 tends to be increased in a dose-proportional manner in the dose range of 0.3-200 mg.

CONCLUSIONS

A single intravenous dose of LC28-0126 was safe and well tolerated up to 200 mg. Furthermore, LC28-0126 demonstrated a predictable pharmacokinetic profile after a single intravenous infusion of doses ranging from 0.3 to 200 mg.

Altered serum creatine kinase level and cardiac function in ischemia-reperfusion injury during percutaneous coronary intervention

Background

Myocardial ischemia-reperfusion injury (MIRI) resulting from primary percutaneous coronary intervention (PCI) for acute myocardial infarction (AMI) is considered harmful to the patient, but its clinical significance remains unclear. This study explored the relationship of cardiac function examined by echocardiography and serum creatine kinase (CK) and CK-MB levels with MIRI in a cohort of Chinese AMI patients.

Material/Methods

We retrospectively analysed the clinical and angiographic data in 228 AMI patients in whom the infarct-related artery (IRA) was successfully recanalized by primary PCI. Cardiac function was evaluated by use of echocardiography before discharge from hospital.

Results

The in-hospital mortality rate in the MIRI group was 13.4% (16/119), which was significantly higher than the 4.6% (5/109) mortality rate in the non-MIRI group (P=0.021). The median of peak serum CK level was remarkably lower in the suppression-type MIRI group than in the non-MIRI group. There were no significant differences in the peak serum CK or CK-MB levels between the irritation-type MIRI group and the non-MIRI group. The peak CK and CK-MB levels were significantly higher in the no-reflow-type MIRI group than in the non-MIRI group. Left ventricular ejection fraction in the no-reflow-type MIRI group was significantly lower than in the non-MIRI group; left ventricular end-diastolic volume was significantly higher than in the irritation-type MIRI subgroup; and left ventricular end-systolic volume was greater than that in non-MIRI group and suppression-type MIRI group.

Conclusions

MIRI (especially the no-reflow type) may lead to acute hemodynamic disorders and increase the mortality rate. However, suppression- and irritation-type MIRI may imply the existence of surviving myocardium.

Determinants and prognostic implications of reperfusion injury during primary percutaneous coronary intervention in Chinese patients with acute myocardial infarction

BACKGROUND

The poor clinical outcome in acute myocardial infarction (AMI) patients undergoing primary percutaneous coronary intervention (PCI) has been attributed to myocardial ischemia-reperfusion injury (MIRI).

OBJECTIVE

This study aimed to identify the predictive factors of MIRI during PCI in Chinese AMI patients with or without ST-segment elevation.

METHODS

Clinical and angiographic data of 228 patients in whom the infarct-related artery (IRA) was successfully recanalized by primary PCI were retrospectively analyzed. Multiple logistic regressions were used.

RESULTS

Compared with non-MIRI group (n=109), patients with MIRI (n=119) were characterized by more inferior infarct location, shorter ischemic duration, more frequently right coronary artery as IRA, more lesion vessels, more often thrombolysis in myocardial infarction (TIMI) 0 flow in IRA prior to PCI, less preinfarction angina, and more renal insufficiency. Ischemic time<or=6 hours (p=0.014), inferior infarct location (p=0.006), and initial antegrade flow in IRA<or=TIMI grade 1 (p=0.028) were independent risk factors for MIRI. Other risk factors included multivessel lesions (p=0.063) and renal insufficiency (p=0.067). Only preinfarction angina was a protective factor (p=0.005).

CONCLUSIONS

The factors promoting MIRI during primary PCI includes short ischemic time from AMI onset to IRA recanalization, inferior infarct location, low IRA antegrade flow prior to PCI, multivessel lesions, and renal insufficiency, whereas preinfarction angina is a protective factor attenuating MIRI.

Oxidation of multiple methionine residues impairs rapid sodium channel inactivation

Reactive oxygen species (ROS) readily oxidize the sulfur-containing amino acids cysteine and methionine (Met). The impact of Met oxidation on the fast inactivation of the skeletal muscle sodium channel Na(V)1.4 expressed in mammalian cells was studied by applying the Met-preferring oxidant chloramine-T or by irradiating the ROS-producing dye Lucifer Yellow in the patch pipettes. Both interventions dramatically slowed down inactivation of the sodium channels. Replacement of Met in the Ile-Phe-Met inactivation motif with Leu (M1305L) strongly attenuated the oxidizing effect on inactivation but did not eliminate it completely. Mutagenesis of Met1470 in the putative receptor of the inactivation lid also markedly diminished the oxidation sensitivity of the channel, while that of other conserved Met residues in intracellular linkers connecting the membrane-spanning segments (442, 1139, 1154, 1316, 1469) were of minor importance. The results of mutagenesis, assays of other Na(V) channel isoforms (Na(V)1.2, Na(V)1.5, Na(V)1.7), and the kinetics of the oxidation-induced removal of inactivation collectively indicate that multiple Met residues need to be oxidized to completely impair inactivation. This arrangement using multiple Met residues confers a finely graded oxidative modulation of Na(V) channels and allows organisms to adapt to a variety of oxidative stress conditions, such as ischemic reperfusion.

Functional consequences of methionine oxidation of hERG potassium channels

Reactive species oxidatively modify numerous proteins including ion channels. Oxidative sensitivity of ion channels is often conferred by amino acids containing sulfur atoms, such as cysteine and methionine. Functional consequences of oxidative modification of methionine in human ether à go-go related gene 1 (hERG1), which encodes cardiac I(Kr) channels, are unknown. Here we used chloramine-T (ChT), which preferentially oxidizes methionine, to examine the functional consequences of methionine oxidation of hERG channels stably expressed in a human embryonic kidney cell line (HEK 293) and native hERG channels in a human neuroblastoma cell line (SH-SY5Y). ChT (300 microM) significantly decreased whole-cell hERG current in both HEK 293 and SH-SY5Y cells. In HEK 293 cells, the effects of ChT on hERG current were time- and concentration-dependent, and were markedly attenuated in the presence of enzyme methionine sulfoxide reductase A that specifically repairs oxidized methionine. After treatment with ChT, the channel deactivation upon repolarization to -60 or -100 mV was significantly accelerated. The effect of ChT on channel activation kinetics was voltage-dependent; activation slowed during depolarization to +30 mV but accelerated during depolarization to 0 or -10mV. In contrast, the reversal potential, inactivation kinetics, and voltage-dependence of steady-state inactivation remained unaltered. Our results demonstrate that the redox status of methionine is an important modulator of hERG channel.

Nutraceutics and delivery systems

Medical treatment has been shifted to being more prophylactic as a recent trend. Postgenomic research has unveiled the fact that nutritional intervention has been strongly associated with genetic expressions, which are responsible for a variety of biological functions. Based on these findings, the prophylactic effects of dietary supplement and nutrient have been enthusiastically investigated. Preventing or retarding the onset of diseases has become a more attractive and cost effective strategy in the medical arena. Among other approaches to prevent diseases, antioxidants, which are found in many phytochemicals, have received much attention. However, most natural antioxidants such as alpha-tocopherol, ascorbic acid and others are biologically unstable, poorly soluble in water, and poorly distributed to target sites. Because of these shortcomings further prophylactic applications of dietary supplements have stagnated. This is partially due to a lack of basic awareness of drug delivery system for dietary supplements and nutrients. In this article, we strongly advocate serious consideration of the bioavailability of dietary supplements. Currently, there are some challenging works to improve their bioavailability using delivery systems such as liposomal formulations. We will discuss the target molecules of dietary supplements for prevention of diseases and also introduce the pioneering works of delivery systems for dietary supplements to promote their therapeutic value.

Usefulness of frequent arrhythmias after epicardial recanalization in anterior wall acute myocardial infarction as a marker of cellular injury leading to poor recovery of left ventricular function

Ventricular arrhythmias are associated with epicardial reperfusion but may also be a sign of cellular injury, which affects recovery of left ventricular (LV) function. To assess the correlation between reperfusion arrhythmias and the change in LV function after the acute phase in reperfused acute myocardial infarction (AMI), 62 patients with reperfused anterior wall AMI were studied. All patients underwent 24-hour Holter recording, echocardiography, and coronary angiography during the acute phase of AMI. Echocardiography was repeated at 1 to 2 months after AMI. Correlations between ventricular arrhythmias in the reperfusion phase and the change in LV wall motion score (WMS) during follow-up were studied. The number of reperfusion arrhythmias was significantly higher in patients with further deterioration of LV function; there were 5-, 14-, 131-, and 11-fold increases in isolated premature ventricular complexes (PVCs), PVCs in couplets, PVCs in bigeminy, and total PVCs, respectively, in patients with further increases in WMS after the acute phase. The incidence of repetitive, frequent, and early accelerated idioventricular rhythms (AIVRs) was correlated significantly with the change in LV function, with 129- and 105-fold increases in numbers of early AIVRs and total AIVRs, respectively, in patients with further worsening of LV function during follow-up. The incidence and the number of long-lasting nonsustained ventricular tachycardias as well as the number of rapid ventricular tachycardias and total ventricular tachycardia episodes were also correlated significantly with further deterioration. Thus, frequent arrhythmias associated with epicardial reperfusion strongly correlate with further worsening of LV function after the acute phase of AMI. This supports the hypothesis that these reperfusion arrhythmias are probably a noninvasive marker of cellular injury.

Intravenous administration of MEK inhibitor U0126 affords brain protection against forebrain ischemia and focal cerebral ischemia

Brain subjected to acute ischemic attack caused by an arterial blockage needs immediate arterial recanalization. However, restoration of cerebral blood flow can cause tissue injury, which is termed reperfusion injury. It is important to inhibit reperfusion injury to achieve greater brain protection. Because oxidative stress has been shown to activate mitogen-activated protein kinases (MAPKs), and because oxidative stress contributes to reperfusion injury, MAPK may be a potential target to inhibit reperfusion injury after brain ischemia. Here, we demonstrate that reperfusion after forebrain ischemia dramatically increases phosphorylation level of extracellular signal-regulated kinase 2 (ERK2) in the gerbil hippocampus. In addition, i.v. administration of U0126 (100-200 mg/kg), a specific inhibitor of MEK (MAPK/ERK kinase), protects the hippocampus against forebrain ischemia. Moreover, treatment with U0126 at 3 h after ischemia significantly reduces infarct volume after transient (3 h) focal cerebral ischemia in mice. This protection is accompanied by reduced phosphorylation level of ERK2, substrates for MEK, in the damaged brain areas. Furthermore, U0126 protects mouse primary cultured cortical neurons against oxygen deprivation for 9 h as well as nitric oxide toxicity. These results provide further evidence for the role of MEK/ERK activation in brain injury resulting from ischemia/reperfusion, and indicate that MEK inhibition may increase the resistance of tissue to ischemic injury.