Maintenance of the myocardial thiol pool by N-acetylcysteine

Effect of N-acetylcysteine on cardiac injury and oxidative stress after abdominal aortic aneurysm repair: a randomized controlled trial

BACKGROUND

Several studies have reported that the antioxidant properties of N-acetylcysteine (NAC) can provide cardiac protection through scavenging of free radicals. The present study was aimed to assess the efficacy of NAC for cardiac protection in patients undergoing elective abdominal aortic aneurysm (AAA) repair.

METHODS

Fifty adult patients undergoing (AAA) repair were randomly allocated to receive NAC infusion (n = 25) or placebo infusion (n = 25). NAC infusion in group I (NAC group) was started at a rate of 0.3 mg/kg/min intravenously during surgery then decreased to a rate of 0.2 mg/kg/min for 24 h post-operatively. Group II (placebo group) received an equivalent rate of placebo infusion. The following parameters: myocardial-specific protein troponin-I, creatine phosphokinase-MB (CPK-MB), plasma pro-inflammatory cytokines [tumour necrosis factor-α (TNF-α) and interleukin (IL)-1β], were assessed at the following time points: preoperatively and at 1 h, 12 h, 24 h, 48 h, and 96 h after surgery. Furthermore, serum malondialdehyde (MDA) and total antioxidant capacity (TAC) were measured preoperatively as a baseline, during aortic clamping, 30 min after declamping, at the end of surgery, 2 h after surgery, 12 h after surgery, and 24 h after surgery.

RESULTS

NAC infusion patients had significantly lower post-operative concentrations of myocardial-specific protein [cTnI, CPK-MB] and pro-inflammatory cytokines [TNF-α, IL-1β]. In addition, MDA level was less and TAC was higher in patients who received NAC infusion.

CONCLUSION

NAC infusion provided cardiac protection through scavenging of oxygen free radicals.

Effects of cadmium on cardiac metallothionein induction and ischemia–reperfusion injury in rats

Myocardial ischemia–reperfusion injury is associated with an imbalance between the formation and the scavenging of reactive oxygen species. In this context, the protective role of the antioxidant metallothionein, a thiol-rich protein that is induced in different organs in response to heavy metals and oxidative conditions, has mainly been investigated in metallothionein-knockout mice or metallothionein-overexpressing mice. The aim of this study was to evaluate whether the administration of cadmium has a protective effect against cardiac ischemia–reperfusion injury and whether this is associated with induction of in vivo cardiac metallothionein. Forty-eight hours after an injection of 0, 1, or 2 mg/kg cadmium, isolated perfused rat hearts were submitted to 30 min of total global ischemia and 30 min of reperfusion.   The ischemia–reperfusion sequence was associated with a significant decrease in cardiac metallothionein levels. Pretreatment with cadmium at a dose of 2 mg/kg (i) prevented this decrease and (ii) improved the postischemic recuperation of the coronary flow, the ventricular developed pressure, and therefore, the global postischemic functional recovery. These results showed that pretreatment of rats with 2 mg/kg cadmium induced cardioprotection against ischemia–reperfusion injuries, perhaps through an in vivo metallothionein induction that may be related to a metal activation of antioxidant systems.

Effect of N-acetylcysteine in attenuating ischemic reperfusion injury in patients undergoing coronary artery bypass grafting with cardiopulmonary bypass

Ischemic reperfusion injury due to oxidative stress remains one of the challenging problems during cardiac surgeries. The imbalance in the production of free radicals and antioxidants in vivo determines the extent of oxidative stress. The use of antioxidants in cardioplegia has become an important strategy to salvage the myocardium from the attack of these radicals. The objective of this study was to analyze the cardioprotective effect of N-acetylcysteine (NAC) on early reperfusion injury in patients undergoing coronary artery bypass grafting using biochemical markers. Fifty-three patients with left ventricular ejection fraction >0.4 scheduled for coronary artery bypass grafting with cardiopulmonary bypass were selected and divided into two groups. The first group of patients (n=25) received isothermic cardioplegia alone, whereas the second group of patients (n=28) received cardioplegia enriched with NAC (50mg/kg body weight). The free radicals, antioxidants, cardiac troponin I, and hemodynamic and clinical properties of the patients were preoperatively and postoperatively evaluated at five different time intervals. Malondialdehyde level as a measure of free radicals was significantly lower in the NAC-enriched group during reperfusion (p<0.05) and after 12 hr (p<0.05) and 24hr (p<0.001) of surgery. All the antioxidants were elevated in the test group during the reperfusion period (p<0.01). A significant improvement (p=0.001) in the postoperative ejection fraction was noted in the test group. No significant differences were observed between the groups in the level of cardiac troponin I (p=not significant). The use of NAC in patients undergoing coronary artery bypass grafting using cardiopulmonary bypass decreased oxidative stress substantially. However, it did not lead to improvement in the level of cardiac troponin I, a marker of myocardial injury, in our study. Hence, the cardioprotective effect of NAC and the adaptation of the myocardium to oxidative stress should be extensively studied.

The protective effect of N-acetylcysteine against cyclosporine A-induced hepatotoxicity in rats

The immunosuppressive agent cyclosporine A (CsA) has been reported to exert measurable hepatotoxic effects. One of the causes leading to hepatotoxicity is thought to be reactive oxygen radical formation. The aim of this study was to investigate the effects of N-acetylcysteine (NAC) treatment on CsA-induced hepatic damage by both analysing superoxide dismutase (SOD), glutathione peroxidase (GSH-Px), aspartate aminotransferase (AST) and alanine transaminase (ALT) activities with malondialdehyde (MDA) and nitric oxide (NO) levels, and using an histological approach. CsA administration produced a decrease in hepatic SOD activity, and co-administration of NAC with CsA resulted in an increase in SOD activity. MDA and NO levels increased in the CsA group and NAC treatment prevented those increases. A significant elevation in serum AST and ALT activities was observed in the CsA group, and when NAC and CsA were co-administered, the activities of AST and ALT were close to the control levels. CsA treatment caused evident morphological alterations. Control rats showed no abnormality in the cytoarchitecture of the hepatic parenchyma. The co-administration of NAC with CsA showed no signs of alteration and the morphological pattern was almost similar to the control group. In conclusion, CsA induced liver injury and NAC treatment prevented the toxic side effects induced by CsA administration through the antioxidant and radical scavenging effects of NAC.

Do N-acetylcystein, beta-glucan, and coenzyme Q10 mollify myocardial ischemia-reperfusion injury?

BACKGROUND

N-acetylcysteine, beta-glucan, and coenzyme Q10 have been shown to have antioxidant and anti-inflammatory effects on reperfusion injury. The aim of our study was to determine and evaluate the effects of these agents on myocardial ischemia-reperfusion injury.

METHODS

Forty-four New Zealand white rabbits, all female, weighing 2.4 to 4.1 kg (mean, 3.6 kg) were used in the study. Four study groups of 11 animals were arranged by randomization. The groups were the control group (group C), a group premedicated with coenzyme Q10 (group Q), a group premedicated with beta-glucan (group betaT), and a group premedicated with N-acetylcysteine (group N). After exploration of the heart, a basal myocardial biopsy was taken from the anteroapical left ventricle, and the first blood sampling was done before ischemia. For the ischemia-reperfusion experiments, the major left anterior descending artery was occluded after baseline measurements. After a 45-minute transient ischemic period, the heart was perfused for 120 minutes. After perfusion, the second myocardial biopsy was taken from the anteroapical left ventricle, and the second blood sampling was done. Blood and tissue analysis were performed and evaluated statistically.

RESULTS

Baseline and reperfusion levels of glutathione peroxidase, superoxide dismutase, malonyldialdehyde, and nitric oxide changed significantly. While malonyldialdehyde levels increased in group C, they decreased in the other study groups (P =.001). The increases in glutathione peroxidase and superoxide dismutase levels were significant in all groups except group C (P =.0001 and P <.05, respectively). Levels of nitric oxide were found to be decreased in group C, whereas they increased in the other groups (P =.001).

CONCLUSION

Antioxidant medication may help in lowering the risk of myocardial ischemia-reperfusion injury. All the medications in our study are shown to have effective roles in preventing ischemia-reperfusion injury to some extent through their antioxidant properties.

Protective effects of antioxidant medications on limb ischemia reperfusion injury

BACKGROUND

N-acetylcysteine, beta-glucan, and coenzyme Q(10) were shown to have antioxidant and anti-inflammatory effects on reperfusion injury. The aim of our study was to determine and evaluate the effects of these agents on ischemia reperfusion injury of limb.

MATERIAL AND METHOD

Forty-four New Zealand white rabbits, all female, weighing between 2.3 to 4.2 (mean 3.8) kg, were used in the study. Four study groups were arranged of 11 animals each, by randomization. The first group was the control group (Group C), the other groups were the Group Q, which was medicated with coenzyme Q10, the Group betaG, which was medicated with beta-glucan, and the Group N, medicated with N-acetylcysteine. After baseline measurements, for the ischemia-reperfusion experiments, common iliac artery was clamped and collateral flow was occluded by a rubber arterial tourniquet wrapped around the thigh at the proximal third of the leg. After 60 min of transient ischemic period, the limb was perfused for 180 min. After perfusion, biopsy was taken from the adductor magnus muscle. Second blood sampling was done after reperfusion period. Blood and tissue analysis were done and evaluated statistically.

RESULTS

Baseline and post-reperfusion levels of glutathione peroxidase (GPx), super oxide dismutase (SOD), malonyldialdehyde (MDA), and nitric oxide (NO) changed significantly. While MDA levels increased in the control group, it decreased in the other study groups. The increase in GPx and SOD levels were significant in all groups except the control group. Levels of NO were found to have decreased in the control group, whereas it had increased in the other groups.

CONCLUSION

Antioxidant medication may help lowering limb ischemia reperfusion injury. All mentioned medications in our study are shown to be able to have an effective role for preventing ischemia reperfusion injury to some extent through their antioxidant properties.

Effect of intravenous N-acetylcysteine on outcomes after coronary artery bypass surgery: A randomized, double-blind, placebo-controlled clinical trial

OBJECTIVE

N-acetylcysteine, a potent anti-inflammatory and antioxidant agent, is known to decrease the production of reactive oxygen species after cardiac surgery. The objective of this study was to evaluate the effects of intravenous N-acetylcysteine on clinical and biochemical outcomes after coronary artery bypass surgery with cardiopulmonary bypass.

METHODS

One hundred patients (mean age 60.5 years, range 43-78 years, 89% male) undergoing coronary artery bypass grafting at the Montreal Heart Institute were randomized to receive either N-acetylcysteine (600 mg orally the day before and the morning of the operation, a bolus of 150 mg/kg of intravenous N-acetylcysteine before skin incision, followed by perfusion at 12.5 mg x kg(-1) x h(-1) over 24 hours; n = 50) or placebo (n = 50). The patients and clinical team were blinded to group assignments. Preoperative characteristics were similar between the two groups. Postoperative clinical data (death, myocardial infarction, low-output syndromes, arrhythmias, bleeding, transfusion requirements, and intensive care unit and hospital lengths of stay) and biochemical markers (creatine kinase MB, troponin T, creatinine, hemoglobin, and platelet levels) were evaluated serially over 4 days.

RESULTS

Clinical outcomes were not significantly different between the two groups with regard to the incidence of death, myocardial infarction, bleeding, transfusion requirements, intubation time, and hospital length of stay. No differences were found in postoperative biochemical markers (troponin T, creatine kinase MB, creatinine, hemoglobin, and platelets) between the groups. No differences were observed between the groups in interleukin-6 production (P = not significant).

CONCLUSIONS

Prophylactic use of N-acetylcysteine in patients undergoing coronary artery bypass grafting with cardiopulmonary bypass does not lead to improvement in clinical results or biochemical markers. Further strategies to decrease reperfusion injury should be devised.

Age-related increase in 4-hydroxynonenal adduction to rat heart alpha-ketoglutarate dehydrogenase does not cause loss of its catalytic activity

4-hydroxynonenal (HNE), a product of omega-6 polyunsaturated fatty acid peroxidation, impairs mitochondrial respiration in vitro by adducting the alpha-ketoglutarate dehydrogenase complex (KGDC) and inhibiting its activity. The present study seeks to define whether aging increases HNE adduction to rat heart KGDC, and whether such adduction impacts KGDC activity. We found that hearts from old rats exhibit significantly (p< or =0.01) higher HNE-modified mitochondrial proteins when compared with those from young rats. Among these proteins, dihydrolipoamide succinyltransferase, the E2k component of KGDC, was most markedly modified (p< or =0.01) by HNE with age. As opposed to that seen in vitro, no significant change in electrophoretic mobility or impairment in enzyme activity was observed. On the contrary, KGDC activity increased onefold (p< or =0.01) in old rats, suggesting that the aging myocardium is not affected by HNE adduction or compensates for such damage. Further analysis revealed that heightened KGDC activity was not due to increased protein content or gene expression, but correlates with a lower Km for alpha-ketoglutarate. Thus, contrary to that observed in vitro, the measurement of HNE-KGDC adduct in rat heart is more relevant as a marker of age-related protein oxidation than a factor of mitochondrial dysfunction.

Attenuation of ischemia/reperfusion injury by N-acetylcysteine in a rat hind limb model

BACKGROUND

Ischemia/reperfusion is a complex set of events with severe pathologic consequences. Reperfusion initiates both the local and systemic damage in part through rapid oxygen generation. N-acetylcysteine (NAC) is a scavenger of free radical species, inhibits neutrophil accumulation, acts as a vasodilator and also improves microcirculation. In present study, we examined the protective effect of NAC in a rat hind limb ischemia/ reperfusion model. Dimethyl-sulfoxide (DMSO), a well-known antioxidant was also tested for comparison.

MATERIALS AND METHODS

Ischemia was induced for 4 h by vascular clamping and followed by 1 h of reperfusion. Muscle injury was evaluated in 3 groups as a saline group (control), DMSO group, and NAC group. Plasma levels of creatine kinase, lactate dehydrogenase, thiobarbituric acid reactive substances (TBARS), and blood HCO(3), as well as muscle tissue TBARS, were measured at the end of reperfusion. Muscle tissue samples were taken for histological evaluation.

RESULTS

DMSO and NAC group showed significant amelioration of plasma CPK (P < 0.05, P < 0.05), plasma TBARS (P < 0.05, P < 0.05), and muscle tissue TBARS (P < 0.05, P < 0.05) compared with the control group. Similarly, neutrophil infiltration in DMSO and NAC groups were significantly less prominent than the control group (P < 0.01, P < 0.01).

CONCLUSIONS

These results show that NAC improved effectively ischemia reperfusion injury in a rat hind limb model.

L-cysteine prevents oxidation-induced block of the cardiac Na+ channel via interaction with heart-specific cysteinyl residues in the P-loop region

The present study investigated the protective effects of L-cysteine on the oxidation-induced blockade of Na+ channel a-subunits, hH1 (cardiac) and hSkM1 (skeletal), expressed in COS7 cells. Na+ currents were recorded by the whole-cell patch clamp technique (n = 3-7). L-cysteine alone blocked hH1 and hSkM1 in a dose-dependent manner, with saturating L-cysteine block at 3,000 micromol/L. Hg2+, a potent sulfhydryl oxidizing agent, blocked hH1 with a time to 50% inhibition (Time50%) of 20s. Preperfusion of COS7 cells with 100 micromol/L L-cysteine significantly slowed the Hg2+ block of hH1 (Time50% = 179 s). L-cysteine did not prevent Hg2+ block of hSkM1 (Time50% = 37s) or the C373Y hH1 mutant (Time50% = 43s). As for other sulfo-amino acids, homocysteine prevented the Hg2+ block of hH1, with the Time50% (70s) being significantly smaller than that of L-cysteine, whereas methionine did not prevent the Hg2+ block of hH1. L-cysteine did not prevent the Cd2+ block of hH1. These results indicate that L-cysteine selectively acts on heart-specific Cys373 in the P-loop region of hH1 to prevent Cys373 from the oxidation-induced sulfur-Hg-sulfur bridge formation.

N-acetylcysteine in acute cardiology: 10 years later: what do we know and what would we like to know?!

N-acetylcysteine (NAC) is known in a variety of branches of medicine. This paper addresses in detail the action of NAC as it is emerging from research and clinical trials over the past decade in cardiology, giving rise to new concepts. The result is a process resembling creation of a mosaic from individual pieces. Also, the role of NAC in acute cardiology, during acute reperfusion in particular, is defined.

N-acetylcysteine pretreatment of cardiac surgery patients influences plasma neutrophil elastase and neutrophil influx in bronchoalveolar lavage fluid

OBJECTIVE

Study of leukocyte activation and release of toxic mediators during extracorporeal circulation (ECC). ECC can be used to study the potential protective effect of a pharmacon against neutrophil-mediated lung injury. Clinical studies have indicated that N-acetylcysteine (NAC) may improve systemic oxygenation and reduce the need for ventilatory support when given to patients with acute lung injury.

DESIGN

Cardiac surgery patients were pretreated with high-dose NAC in order to assess the potential role of NAC to interfere with neutrophil-mediated inflammation and lung injury.

PATIENTS

18 patients who underwent ECC: group 1 (n = 8) no premedication (only placebo); group 2 (n = 10) NAC (72 mg/kg i.v. as a bolus, later 72 mg/kg over 12 h).

MEASUREMENTS AND RESULTS

In group 2, the partial pressure of oxygen in arterial blood/fractional inspired oxygen 4 h after surgery was significantly higher than in group 1 (213 +/- 31 vs 123 +/- 22; p = 0.044). NAC pretreatment prevented an increase in plasma neutrophil elastase activity (18.9 +/- 6.9 vs 49.9 +/- 5.6 ng/ml in group 1 at the end of ECC; p = 0.027). Release of myeloperoxidase (MPO) was not affected (group 1:1105 +/- 225 ng/ml vs group 2:1127 +/- 81 at the end of ECC; p = 0.63). At the end of ECC, total antigenic human neutrophil elastase (group 1:671 +/- 72 ng/ml vs group 2:579 +/- 134; p = 0.37) and complex formation between elastase and alpha 1-proteinase inhibitor were no different in the two groups. There were no significant difference in cellular composition and mediators in the lavage fluid, although values for total number of neutrophils, elastase, MPO and interleukin-8 were lower in group 2.

CONCLUSION

Pretreatment with NAC may prevent lung injury by diminishing elastase activity. Since the release of mediators, especially MPO, is not affected, this diminished activity of elastase may be achieved by enhanced inactivation by antiproteases after initial treatment.

Ischemic heart disease and antioxidants: mechanistic aspects of oxidative injury and its prevention

The disease state of myocardial ischemia results from a hypoperfusion-induced insufficiency of heart-muscle oxidative metabolism due to inadequate coronary circulation. Myocardial ischemia is an important, lifespan-limiting medical problem and a major economic health-care concern. Reperfusion, although avidly pursued in the clinic as essential to the ultimate survival of acutely ischemic heart muscle, may itself carry an injury component. Cardiac reperfusion injury appears to reflect, at least in part, an oxidant burden established upon reoxygenation of ischemic myocardium. Laboratory evidence demonstrates that oxidative stress to the heart-muscle cell (cardiomyocyte) can elicit the three known types of ischemia-reperfusion injury that directly affect the myocardium: arrhythmia, stunning, and infarction. The limited clinical occurrence of serious reperfusion arrhythmias has restricted the importance of antioxidants as antiarrhythmic agents against this form of myocardial ischemia-reperfusion damage. Despite the utmost clinical significance of lethal cardiomyocyte injury as a negative prognostic indicator for the ischemic heart-disease patient, inconsistent results of antioxidant interventions in reducing infarct size have somewhat tempered interest in antioxidant infarct trials. By contrast, the negative clinical consequences of stunning may indeed be preventable by utilizing antioxidants to help restore postischemic cardiac pump function. Several as yet unanswered questions remain regarding oxidative stress in the reperfused heart, its significance to cardiomyocyte damage, and its ability to elicit specific postischemic myocardial derangements. Targeted mechanistic studies are required to address these questions and to define the pathogenic role of oxidative stress (and, hence, the therapeutic potential of antioxidant intervention) in myocardial ischemia-reperfusion injury. The overall aim of current research in this area is to enable the cardiac surgeon/cardiologist to advance beyond the largely palliative drugs now available for management of the coronary heart-disease patient and attack directly the pathogenic determinants of heart-muscle ischemia-reperfusion injury. Optimal use of antioxidants may help address this important medical need.

Malondialdehyde and glutathione production in isolated perfused human and rat hearts

A number of studies show the relation between oxygen-derived free radicals and cardiac ischemia/reperfusion injury. However, little is known about oxidative stress in the human heart, which can be measured by oxidized glutathione (GSSG) and malondialdehyde (MDA) formation. Furthermore, data on MDA production by rat hearts are controversial, possibly because of the use of the aspecific thiobarbituric acid assay. Therefore, GSSG and MDA were measured, with colorimetric and high-performance liquid chromatographic assays, respectively, in buffer-perfused explanted human hearts and normal rat hearts made temporarily ischemic. Human hearts received cardioplegia; rat hearts were studied in a control and an ischemic group with or without cardioplegia. Baseline GSSG release was < 0.01 nmol.min-1.g wet wt-1 in both species. During reperfusion, GSSG release from human hearts and from ischemic and cardioplegic/ischemic rat hearts peaked at 0.24 +/- 0.12, 1.1 +/- 0.4, and 0.19 +/- 0.04 nmol.min-1.g-1, respectively. MDA was undetectable (< 0.02 nmol.min-1.g-1) in the effluent of both species and in human hearts (< 4 nmol/g protein). Rat heart reduced glutathione levels decreased 32% as a consequence of cardioplegia and ischemia. Cardioplegia induced a 41% (P = .08) decrease in rat heart MDA content, whereas cumene hydroperoxide increased it 3.6 times (P < .01). Thus, after ischemia human and rat hearts release GSSG, indicating that oxidative stress has occurred. Apparently, lipid peroxidation takes place in normal rat hearts, decreases after cardioplegia, but does not increase after ischemia/reperfusion. Human hearts lack MDA under normoxic and ischemic conditions. This novel finding seems to reflect a low MDA-forming potential in both situations.(ABSTRACT TRUNCATED AT 250 WORDS)

The effects of N-methyl butyrohydroxamic acid and other monohydroxamates on reperfusion-induced damage to contractile function in the isolated rat heart

The effects of three novel methyl substituted monohydroxamates N-methyl butyrohydroxamic acid (NMBH), N-methyl acetohydroxamic acid (NMAH) and N-methyl benzohydroxamic acid (NMBzH) against reperfusion induced contractile dysfunction were investigated in the isolated Langendorff-perfused rat heart. All these drugs produced an improved recovery of left ventricular developed pressure (LVDP) compared to control hearts in the order NMBH* (65 +/- 8%) > NMAH (59 +/- 8%) > NMBzH (48 +/- 3%) > control (35 +/- 3%) (mean +/- s.e.), however only the recovery obtained in NMBH treated hearts was significantly different from control hearts (*p > 0.05, Dunnett's test). Both NMAH (98 +/- 10%) and NMBH (84% +/- 8) produced a significant improvement in the recovery of heart rate (control 48 +/- 13%). There was no significant improvement of coronary flow, and NMBzH-treated hearts showed a significant reduction in recovery. The improved recovery in both LVDP and heart rate obtained with NMBH suggests this drug may be effective in attenuating reperfusion-induced contractile dysfunction in the isolated rat heart. Further, a comparison of the structures of the hydroxamates described in this study with the results obtained with desferrioxamine, (a trihydroxamate), and N-methyl hexanoylhydroxamic acid (NMHH) in other studies suggests that the nature of the alkyl chain attached to the carbonyl group of the hydroxamate may contribute to the efficacy of monohydroxamates in attenuating this type of myocardial injury in this model.