Effects of N-acetylcysteine in the rat heart reperfused after low-flow ischemia: evidence for a direct scavenging of hydroxyl radicals and a nitric oxide-dependent increase in coronary flow

Antioxidants for adults with chronic kidney disease

BACKGROUND

Chronic kidney disease (CKD) is a significant risk factor for cardiovascular disease (CVD) and death. Increased oxidative stress in people with CKD has been implicated as a potential causative factor. Antioxidant therapy decreases oxidative stress and may consequently reduce cardiovascular morbidity and death in people with CKD. This is an update of a Cochrane review first published in 2012.

OBJECTIVES

To examine the benefits and harms of antioxidant therapy on death and cardiovascular and kidney endpoints in adults with CKD stages 3 to 5, patients undergoing dialysis, and kidney transplant recipients.

SEARCH METHODS

We searched the Cochrane Kidney and Transplant Register of Studies until 15 November 2022 using search terms relevant to this review. Studies in the Register are identified through searches of CENTRAL, MEDLINE, and EMBASE, conference proceedings, the International Clinical Trials Registry Platform (ICTRP) Search Portal, and ClinicalTrials.gov.

SELECTION CRITERIA

We included all randomised controlled trials investigating the use of antioxidants, compared with placebo, usual or standard care, no treatment, or other antioxidants, for adults with CKD on cardiovascular and kidney endpoints.

DATA COLLECTION AND ANALYSIS

Titles and abstracts were screened independently by two authors who also performed data extraction using standardised forms. Results were pooled using random effects models and expressed as risk ratios (RR) or mean difference (MD) with 95% confidence intervals (CI). Confidence in the evidence was assessed using the Grading of Recommendations Assessment, Development and Evaluation (GRADE) approach.

MAIN RESULTS

We included 95 studies (10,468 randomised patients) that evaluated antioxidant therapy in adults with non-dialysis-dependent CKD (31 studies, 5342 patients), dialysis-dependent CKD (41 studies, 3444 patients) and kidney transplant recipients (21 studies, 1529 patients). Two studies enrolled dialysis and non-dialysis patients (153 patients). Twenty-one studies assessed the effects of vitamin antioxidants, and 74 assessed the effects of non-vitamin antioxidants. Overall, the quality of included studies was moderate to low or very low due to unclear or high risk of bias for randomisation, allocation concealment, blinding, and loss to follow-up. Compared with placebo, usual care, or no treatment, antioxidant therapy may have little or no effect on cardiovascular death (8 studies, 3813 patients: RR 0.94, 95% CI 0.64 to 1.40; I² = 33%; low certainty of evidence) and probably has little to no effect on death (any cause) (45 studies, 7530 patients: RR 0.95, 95% CI 0.82 to 1.11; I² = 0%; moderate certainty of evidence), CVD (16 studies, 4768 patients: RR 0.79, 95% CI 0.63 to 0.99; I² = 23%; moderate certainty of evidence), or loss of kidney transplant (graft loss) (11 studies, 1053 patients: RR 0.88, 95% CI 0.67 to 1.17; I² = 0%; moderate certainty of evidence). Compared with placebo, usual care, or no treatment, antioxidants had little to no effect on the slope of urinary albumin/creatinine ratio (change in UACR) (7 studies, 1286 patients: MD -0.04 mg/mmol, 95% CI -0.55 to 0.47; I² = 37%; very low certainty of evidence) but the evidence is very uncertain. Antioxidants probably reduced the progression to kidney failure (10 studies, 3201 patients: RR 0.65, 95% CI 0.41 to 1.02; I² = 41%; moderate certainty of evidence), may improve the slope of estimated glomerular filtration rate (change in eGFR) (28 studies, 4128 patients: MD 3.65 mL/min/1.73 m², 95% CI 2.81 to 4.50; I² = 99%; low certainty of evidence), but had uncertain effects on the slope of serum creatinine (change in SCr) (16 studies, 3180 patients: MD -13.35 µmol/L, 95% CI -23.49 to -3.23; I² = 98%; very low certainty of evidence). Possible safety concerns are an observed increase in the risk of infection (14 studies, 3697 patients: RR 1.30, 95% CI 1.14 to 1.50; I² = 3%; moderate certainty of evidence) and heart failure (6 studies, 3733 patients: RR 1.40, 95% CI 1.11 to 1.75; I² = 0; moderate certainty of evidence) among antioxidant users. Results of studies with a low risk of bias or longer follow-ups generally were comparable to the main analyses.

AUTHORS' CONCLUSIONS

We found no evidence that antioxidants reduced death or improved kidney transplant outcomes or proteinuria in patients with CKD. Antioxidants likely reduce cardiovascular events and progression to kidney failure and may improve kidney function. Possible concerns are an increased risk of infections and heart failure among antioxidant users. However, most studies were of suboptimal quality and had limited follow-up, and few included people undergoing dialysis or kidney transplant recipients. Furthermore, the large heterogeneity in interventions hampers drawing conclusions on the efficacy and safety of individual agents.

Biodegradable Redox-Responsive AIEgen-Based-Covalent Organic Framework Nanocarriers for Long-Term Treatment of Myocardial Ischemia/Reperfusion Injury

Timely restoration of blood supply after myocardial ischemia is imperative for the treatment of acute myocardial infarction but causes additional myocardial ischemia/reperfusion (MI/R) injury, which has not been hitherto effectively targeted by interventions for MI/R injury. Hence, the development of advanced nanomedicine that can reduce apoptosis of cardiomyocytes while protecting against MI/R in vivo is of utmost importance. Herein, a redox-responsive and emissive TPE-ss covalent organic framework (COF) nanocarrier by integrating aggregation-induced emission luminogens and redox-responsive disulfide motifs into the COF skeleton is developed. TPE-ss COF allows for efficient loading and delivery of matrine, a renowned anti-cryptosporidial drug, which significantly reduces MI/R-induced functional deterioration and cardiomyocyte injury when injected through the tail vein into MI/R models at 5 min after 30 min of ischemia. Moreover, TPE-ss COF@Matrine shows a drastic reduction in cardiomyocyte apoptosis and improvements in cardiac function and survival rate. The effect of the TPE-ss COF carrier is further elucidated by enhanced cardiomyocyte viability and triphenyltetrazolium chloride staining in vitro. This work demonstrates the cardioprotective effect of TPE-ss COFs for MI/R injury, which unleashes the immense potential of using COFs as smart drug carriers for the peri-reperfusion treatment of ischemic heart disease with low cost, high stability, and single postoperative intervention.

The Clinical Efficacy of N-Acetylcysteine in the Treatment of ST Segment Elevation Myocardial Infarction

The aim of this study was to evaluate the clinical efficacy of N-acetylcysteine (NAC) in the treatment of ST segment elevation myocardial infarction (STEMI).PubMed, EMBASE, Cochrane Library, and Web of Science were searched systematically from the establishment of the database to June 2020. Two researchers independently completed literature screening and data extraction and conducted a meta-analysis.Nine articles including 1419 patients were enrolled. Meta-analysis showed that all-cause mortality [RR = 0.56, 95%CI (0.33, 0.93), P = 0.02], occurrence of major adverse cardiovascular events (MACE) [RR = 0.63, 95%CI (0.47, 0.85), P = 0.002], and myocardial enzyme hs-TnT level [SMD = -0.42, 95%CI (-0.71, -0.13), P = 0.005] were significantly lower in patients with STEMI treated with NAC than those in the control group. There was no significant difference between the NAC group and the control group in new congestive heart failure [RR = 0.94, 95%CI (0.48, 1.82), P = 0.84], ejection fraction [MD = 2.00, 95%CI (-0.59, 4.60), P = 0.13], and CK-MB [SMD = -0.18, 95%CI (-0.47, 0.11), P = 0.23]. There was no significant difference in the occurrence of adverse reactions between the NAC group and the control group [RR = 1.04, 95%CI (0.57-1.89), P = 0.90].NAC can reduce the all-cause mortality and MACE cases of STEMI.

Progression of heart failure is attenuated by antioxidant therapy with N-acetylcysteine in myocardial infarcted female rats

This study investigated the therapeutic potential of N-acetylcysteine (NAC) in the treatment of heart failure in female rats. Myocardial infarcted (MI) rats were given NAC (250 mg/kg/day p.o.) during 28 days after surgery (MI + NAC) or vehicle (MI + Placebo), and sham-operated rats received the same treatments (Sham + NAC and Sham + Placebo). Electrocardiographic and echocardiographic analyses were performed in the last week of treatment. Cardiac mRNA levels of types I and II superoxide dismutase (SOD), catalase, types I and III glutathione peroxidase (GPX), nerve growth factor (NGF), β1-adrenergic receptor (β1ADR), and type 2 muscarinic receptor (M2R) were assessed. Cardiac levels NADPH oxidase (NOX) activity_, total content of reduced thiols, and SOD, GPX, and catalase activity were assessed. Compared to MI + Placebo group, MI + NAC group exhibited decreased NOX activity, increased content of reduced thiols, increased GPX activity, and normalized GPX III mRNA levels (p < 0.05). Heart and lung weights, left ventricular (LV) end-diastolic volume and left atrium/aorta ratio were decreased, while LV posterior wall thickness and ejection fraction were increased in MI + NAC group versus MI + Placebo rats (p < 0.05). Power density of low frequency band was decreased, while power density of high frequency and the root mean square of the successive differences were increased in MI + NAC rats versus MI + Placebo (p < 0.05). These findings indicate that NAC promotes therapeutic effects in the progression of MI-induced heart failure in female rats.

Myocardial reperfusion injury and oxidative stress: Therapeutic opportunities

Acute myocardial infarction (AMI) is the leading cause of death worldwide. Its associated mortality, morbidity and complications have significantly decreased with the development of interventional cardiology and percutaneous coronary angioplasty (PCA) treatment, which quickly and effectively restore the blood flow to the area previously subjected to ischemia. Paradoxically, the restoration of blood flow to the ischemic zone leads to a massive production of reactive oxygen species (ROS) which generate rapid and severe damage to biomolecules, generating a phenomenon called myocardial reperfusion injury (MRI). In the clinical setting, MRI is associated with multiple complications such as lethal reperfusion, no-reflow, myocardial stunning, and reperfusion arrhythmias. Despite significant advances in the understanding of the mechanisms accounting for the myocardial ischemia reperfusion injury, it remains an unsolved problem. Although promising results have been obtained in experimental studies (mainly in animal models), these benefits have not been translated into clinical settings. Thus, clinical trials have failed to find benefits from any therapy to prevent MRI. There is major evidence with respect to the contribution of oxidative stress to MRI in cardiovascular diseases. The lack of consistency between basic studies and clinical trials is not solely based on the diversity inherent in epidemiology but is also a result of the methodological weaknesses of some studies. It is quite possible that pharmacological issues, such as doses, active ingredients, bioavailability, routes of administration, co-therapies, startup time of the drug intervention, and its continuity may also have some responsibility for the lack of consistency between different studies. Furthermore, the administration of high ascorbate doses prior to reperfusion appears to be a safe and rational therapy against the development of oxidative damage associated with myocardial reperfusion. In addition, the association with N-acetylcysteine (a glutathione donor) and deferoxamine (an iron chelator) could improve the antioxidant cardioprotection by ascorbate, making it even more effective in preventing myocardial reperfusion damage associated with PCA following AMI.

N-acetyl-cysteine increases cellular dysfunction in progressive chronic kidney damage after acute kidney injury by dampening endogenous antioxidant responses

Oxidative stress and mitochondrial dysfunction exacerbate acute kidney injury (AKI), but their role in any associated progress to chronic kidney disease (CKD) remains unclear. Antioxidant therapies often benefit AKI, but their benefits in CKD are controversial since clinical and preclinical investigations often conflict. Here we examined the influence of the antioxidant N-acetyl-cysteine (NAC) on oxidative stress and mitochondrial function during AKI (20-min bilateral renal ischemia plus reperfusion/IR) and progression to chronic kidney pathologies in mice. NAC (5% in diet) was given to mice 7 days prior and up to 21 days post-IR (21d-IR). NAC treatment resulted in the following: prevented proximal tubular epithelial cell apoptosis at early IR (40-min postischemia), yet enhanced interstitial cell proliferation at 21d-IR; increased transforming growth factor-β1 expression independent of IR time; and significantly dampened nuclear factor-like 2-initiated cytoprotective signaling at early IR. In the long term, NAC enhanced cellular metabolic impairment demonstrated by increased peroxisome proliferator activator-γ serine-112 phosphorylation at 21d-IR. Intravital multiphoton microscopy revealed increased endogenous fluorescence of nicotinamide adenine dinucleotide (NADH) in cortical tubular epithelial cells during ischemia, and at 21d-IR that was not attenuated with NAC. Fluorescence lifetime imaging microscopy demonstrated persistent metabolic impairment by increased free/bound NADH in the cortex at 21d-IR that was enhanced by NAC. Increased mitochondrial dysfunction in remnant tubular cells was demonstrated at 21d-IR by tetramethylrhodamine methyl ester fluorimetry. In summary, NAC enhanced progression to CKD following AKI not only by dampening endogenous cellular antioxidant responses at time of injury but also by enhancing persistent kidney mitochondrial and metabolic dysfunction.

δ-Opioid receptor (DOR) signaling and reactive oxygen species (ROS) mediate intermittent hypoxia induced protection of canine myocardium

Intermittent, normobaric hypoxia confers robust cardioprotection against ischemia-induced myocardial infarction and lethal ventricular arrhythmias. δ-Opioid receptor (DOR) signaling and reactive oxygen species (ROS) have been implicated in cardioprotective phenomena, but their roles in intermittent hypoxia are unknown. This study examined the contributions of DOR and ROS in mediating intermittent hypoxia-induced cardioprotection. Mongrel dogs completed a 20 day program consisting of 5-8 daily, 5-10 min cycles of moderate, normobaric hypoxia (FIO2 0.095-0.10), with intervening 4 min room air exposures. Subsets of dogs received the DOR antagonist naltrindole (200 μg/kg, sc) or antioxidant N-acetylcysteine (250 mg/kg, po) before each hypoxia session. Twenty-four hours after the last session, the left anterior descending coronary artery was occluded for 60 min and then reperfused for 5 h. Arrhythmias detected by electrocardiography were scored according to the Lambeth II conventions. Left ventricles were sectioned and stained with 2,3,5-triphenyl-tetrazolium-chloride, and infarct sizes were expressed as percentages of the area at risk (IS/AAR). Intermittent hypoxia sharply decreased IS/AAR from 41 ± 5 % (n = 12) to 1.8 ± 0.9 % (n = 9; P < 0.001) and arrhythmia score from 4.1 ± 0.3 to 0.7 ± 0.2 (P < 0.001) vs. non-hypoxic controls. Naltrindole (n = 6) abrogated the cardioprotection with IS/AAR 35 ± 5 % and arrhythmia score 3.7 ± 0.7 (P < 0.001 vs. untreated intermittent hypoxia). N-acetylcysteine (n = 6) interfered to a similar degree, with IS/AAR 42 ± 3 % and arrhythmia score 4.7 ± 0.3 (P < 0.001 vs. untreated intermittent hypoxia). Without the intervening reoxygenations, hypoxia (n = 4) was not cardioprotective (IS/AAR 50 ± 8 %; arrhythmia score 4.5 ± 0.5; P < 0.001 vs. intermittent hypoxia). Thus DOR, ROS and cyclic reoxygenation were obligatory participants in the gradually evolving cardioprotection produced by intermittent hypoxia.

The effects of N-acetylcysteine on cisplatin-induced changes of cardiodynamic parameters within coronary autoregulation range in isolated rat hearts

The aim of this study was to evaluate the effects of chronic NAC administration along with cisplatin on cisplatin-induced cardiotoxicity by means of coronary flow (CF), cardiodynamic parameters, oxidative stress markers and morphological changes in isolated rat heart. Isolated hearts of Wistar albino rats (divided into four groups: control, cisplatin, NAC and cisplatin+NAC group) were perfused according to Langendorff technique at constant coronary perfusion pressure starting at 50 and gradually increased to 65, 80, 95 and 110 cm H2O to evaluate cardiodynamic parameters within autoregulation range. Samples of coronary venous effluent (CVE) were collected for determination of CF and biochemical assays, and heart tissue samples for biochemical assays and histopathological examination. Cisplatin treatment decreased CF and heart rate, and increased left ventricular systolic pressure and maximum left ventricular pressure development rate. Cisplatin increased H2O2 and TBARS, but decreased NO2(-) levels in CVE. In tissue samples, cisplatin reduced pathological alterations in myocardium and coronary vessels, with no changes in the amount of total glutathione, as well as in activity of glutathione peroxidase and glutathione reductase. NAC coadministration, by reducing oxidative damage, attenuated cisplatin-induced changes of cardiodynamic and oxidative stress parameters, as well as morphological changes in myocardium and coronary vasculature.

Effects of N-acetylcysteine on the cardiac remodeling biomarkers and major adverse events following acute myocardial infarction: a randomized clinical trial

AIMS

The aims of this study were to evaluate the effects of N-acetylcysteine (NAC) on cardiac remodeling and major adverse events following acute myocardial infarction (AMI).

METHODS

In a prospective, double-blind, randomized clinical trial, the effect of NAC on the serum levels of cardiac biomarkers was compared with that of placebo in 98 patients with AMI. Also, the patients were followed up for a 1-year period for major adverse cardiac events (MACE), including the occurrence of recurrent myocardial infarction, death, and need for target vessel revascularization.

RESULTS

In patients who received NAC, the serum levels of matrix metalloproteinase (MMP)-9 and MMP-2 after 72 h were significantly lower than those in the placebo group (p = 0.014 and p = 0.045, respectively). The length of hospitalization in patients who received NAC was significantly shorter than that in the placebo group (p = 0.024). With respect to MACE, there was a significant difference between those who received NAC (14 %) and those patients on placebo (25 %) (p = 0.024). Re-infarction took place in 4 % of patients in the NAC group as compared with 16.7 % in patients who received placebo (p = 0.007).

CONCLUSION

NAC can be beneficial in preventing early remodeling by reducing the level of MMP-2 and MMP-9. Moreover, NAC decreased the length of hospital stays in patients after AMI. By decreasing MACE, NAC could possibly be introduced as a 'magic bullet' in the pharmacotherapy of patients with AMI. Further studies are needed to elucidate NAC's role in this population.

Reduction of early reperfusion injury with the mitochondria-targeting peptide bendavia

We recently showed that Bendavia, a novel mitochondria-targeting peptide, reduced infarction and no-reflow across several experimental models. The purpose of this study was to determine the therapeutic timing and mechanism of action that underlie Bendavia's cytoprotective property. In rabbits exposed to in vivo ischemia/reperfusion (30/180 min), Bendavia administered 20 minutes prior to reperfusion (0.05 mg/kg/h, intravenously) reduced myocardial infarct size by ∼50% when administered for either 1 or 3 hours of reperfusion. However, when Bendavia perfusion began just 10 minutes after the onset of reperfusion, the protection against infarction and no-reflow was completely lost, indicating that the mechanism of protection is occurring early in reperfusion. Experiments in isolated mouse liver mitochondria found no discernible effect of Bendavia on blocking the permeability transition pore, and studies in isolated heart mitochondria showed no effect of Bendavia on respiratory rates. As Bendavia significantly lowered reactive oxygen species (ROS) levels in isolated heart mitochondria, the ROS-scavenging capacity of Bendavia was compared to well-known ROS scavengers using in vitro (cell-free) systems that enzymatically generate ROS. Across doses ranging from 1 nmol/L to 1 mmol/L, Bendavia showed no discernible ROS-scavenging properties, clearly differentiating itself from prototypical scavengers. In conclusion, Bendavia is a promising candidate to reduce cardiac injury when present at the onset of reperfusion but not after reperfusion has already commenced. Given that both infarction and no-reflow are related to increased cellular ROS, Bendavia's protective mechanism of action likely involves reduced ROS generation (as opposed to augmented scavenging) by endothelial and myocyte mitochondria.

Oxidative stress and nucleic acid oxidation in patients with chronic kidney disease

Patients with chronic kidney disease (CKD) have high cardiovascular mortality and morbidity and a high risk for developing malignancy. Excessive oxidative stress is thought to play a major role in elevating these risks by increasing oxidative nucleic acid damage. Oxidative stress results from an imbalance between reactive oxygen/nitrogen species (RONS) production and antioxidant defense mechanisms and can cause vascular and tissue injuries as well as nucleic acid damage in CKD patients. The increased production of RONS, impaired nonenzymatic or enzymatic antioxidant defense mechanisms, and other risk factors including gene polymorphisms, uremic toxins (indoxyl sulfate), deficiency of arylesterase/paraoxonase, hyperhomocysteinemia, dialysis-associated membrane bioincompatibility, and endotoxin in patients with CKD can inhibit normal cell function by damaging cell lipids, arachidonic acid derivatives, carbohydrates, proteins, amino acids, and nucleic acids. Several clinical biomarkers and techniques have been used to detect the antioxidant status and oxidative stress/oxidative nucleic acid damage associated with long-term complications such as inflammation, atherosclerosis, amyloidosis, and malignancy in CKD patients. Antioxidant therapies have been studied to reduce the oxidative stress and nucleic acid oxidation in patients with CKD, including alpha-tocopherol, N-acetylcysteine, ascorbic acid, glutathione, folic acid, bardoxolone methyl, angiotensin-converting enzyme inhibitor, and providing better dialysis strategies. This paper provides an overview of radical production, antioxidant defence, pathogenesis and biomarkers of oxidative stress in patients with CKD, and possible antioxidant therapies.

The chemistry and biological activities of N-acetylcysteine

BACKGROUND

N-acetylcysteine (NAC) has been in clinical practice for several decades. It has been used as a mucolytic agent and for the treatment of numerous disorders including paracetamol intoxication, doxorubicin cardiotoxicity, ischemia-reperfusion cardiac injury, acute respiratory distress syndrome, bronchitis, chemotherapy-induced toxicity, HIV/AIDS, heavy metal toxicity and psychiatric disorders.

SCOPE OF REVIEW

The mechanisms underlying the therapeutic and clinical applications of NAC are complex and still unclear. The present review is focused on the chemistry of NAC and its interactions and functions at the organ, tissue and cellular levels in an attempt to bridge the gap between its recognized biological activities and chemistry.

MAJOR CONCLUSIONS

The antioxidative activity of NAC as of other thiols can be attributed to its fast reactions with OH, NO2, CO3(-) and thiyl radicals as well as to restitution of impaired targets in vital cellular components. NAC reacts relatively slowly with superoxide, hydrogen-peroxide and peroxynitrite, which cast some doubt on the importance of these reactions under physiological conditions. The uniqueness of NAC is most probably due to efficient reduction of disulfide bonds in proteins thus altering their structures and disrupting their ligand bonding, competition with larger reducing molecules in sterically less accessible spaces, and serving as a precursor of cysteine for GSH synthesis.

GENERAL SIGNIFICANCE

The outlined reactions only partially explain the diverse biological effects of NAC, and further studies are required for determining its ability to cross the cell membrane and the blood-brain barrier as well as elucidating its reactions with components of cell signaling pathways.

Antioxidants for chronic kidney disease

BACKGROUND

Chronic kidney disease (CKD) is a significant risk factor for premature cardiovascular disease and death. Increased oxidative stress in people with CKD has been implicated as a potential causative factor for some cardiovascular diseases. Antioxidant therapy may reduce cardiovascular mortality and morbidity in people with CKD.

OBJECTIVES

To examine the benefits and harms of antioxidant therapy on mortality and cardiovascular events in people with CKD stages 3 to 5; dialysis, and kidney transplantation patients.

SEARCH METHODS

We searched the Cochrane Renal Group's specialised register (July 2011), CENTRAL (Issue 6, 2011), MEDLINE (from 1966) and EMBASE (from 1980).

SELECTION CRITERIA

We included all randomised controlled trials (RCTs) investigating the use of antioxidants for people with CKD, or subsets of RCTs reporting outcomes for participants with CKD.

DATA COLLECTION AND ANALYSIS

Titles and abstracts were screened independently by two authors who also performed data extraction using standardised forms. Results were pooled using the random effects model and expressed as either risk ratios (RR) or mean difference (MD) with 95% confidence intervals (CI).

MAIN RESULTS

We identified 10 studies (1979 participants) that assessed antioxidant therapy in haemodialysis patients (two studies); kidney transplant recipients (four studies); dialysis and non-dialysis CKD patients (one study); and patients requiring surgery (one study). Two additional studies reported the effect of an oral antioxidant inflammation modulator in patients with CKD (estimated glomerular filtration rate (eGFR) 20 to 45 mL/min/1.73 m²), and post-hoc findings from a subgroup of people with mild-to-moderate renal insufficiency (serum creatinine ≥125 μmol/L) respectively. Interventions included different doses of vitamin E (two studies); multiple antioxidant therapy (three studies); co-enzyme Q (one study); acetylcysteine (one study); bardoxolone methyl (one study); and human recombinant superoxide dismutase (two studies).Compared with placebo, antioxidant therapy showed no clear overall effect on cardiovascular mortality (RR 0.95, 95% CI 0.70 to 1.27; P = 0.71); all-cause mortality (RR 0.93, 95% CI 0.76 to 1.14; P = 0.48); cardiovascular disease (RR 0.78, 95% CI 0.52 to 1.18; P = 0.24); coronary heart disease (RR 0.71, 95% CI 0.42 to 1.23; P = 0.22); cerebrovascular disease (RR 0.91, 95% CI 0.63 to 1.32; P = 0.63); or peripheral vascular disease (RR 0.54, 95% CI 0.26 to 1.12; P = 0.10). Subgroup analyses found no evidence of significant heterogeneity based on proportions of males (P = 0.99) or diabetes (P = 0.87) for cardiovascular disease. There was significant heterogeneity for cardiovascular disease when studies were analysed by CKD stage (P = 0.003). Significant benefit was conferred by antioxidant therapy for cardiovascular disease prevention in dialysis patients (RR 0.57, 95% CI 0.41 to 0.80; P = 0.001), although no effect was observed in CKD patients (RR 1.06, 95% CI 0.84 to 1.32; P = 0.63).Antioxidant therapy was found to significantly reduce development of end-stage of kidney disease (ESKD) (RR 0.50, 95% CI 0.25 to 1.00; P = 0.05); lowered serum creatinine levels (MD 1.10 mg/dL, 95% CI 0.39 to 1.81; P = 0.003); and improved creatinine clearance (MD 14.53 mL/min, 95% CI 1.20 to 27.86; P = 0.03). Serious adverse events were not significantly increased by antioxidants (RR 2.26, 95% CI 0.74 to 6.95; P = 0.15).Risk of bias was assessed for all studies. Studies that were classified as unclear for random sequence generation or allocation concealment reported significant benefits from antioxidant therapy (RR 0.57, 95% CI 0.41 to 0.80; P = 0.001) compared with studies at low risk of bias (RR 1.06, 95% CI 0.84 to 1.32; P = 0.63).

AUTHORS' CONCLUSIONS

Although antioxidant therapy does not reduce the risk of cardiovascular and all-cause death or major cardiovascular events in people with CKD, it is possible that some benefit may be present, particularly in those on dialysis. However, the small size and generally suboptimal quality of the included studies highlighted the need for sufficiently powered studies to confirm this possibility. Current evidence suggests that antioxidant therapy in predialysis CKD patients may prevent progression to ESKD; this finding was however based on a very small number of events. Further studies with longer follow-up are needed for confirmation. Appropriately powered studies are needed to reliably assess the effects of antioxidant therapy in people with CKD.

Improved renal recovery with postresuscitation N-acetylcysteine treatment in asphyxiated newborn pigs

Renal injury is one of the severe and common complications that occurs early in neonates with asphyxia, and reactive oxygen species have been implicated to play an important role on its pathogenesis. Improved renal recovery has been shown previously with N-acetyl-l-cysteine (NAC) in various acute kidney injuries. Using a subacute swine model of neonatal hypoxia-reoxygenation (H/R), we examined whether NAC can sustain its beneficial effect on renal recovery for 48 h. Newborn piglets were randomly assigned into a sham-operated group (without H/R, n = 6) and two H/R experimental groups (n = 8 each) with 2 h normocapnic alveolar hypoxia and 1 h 100% oxygen of reoxygenation followed by 21% oxygen for 47 h. Five minutes after reoxygenation, piglets received either normal saline (H/R control) or NAC (150-mg/kg bolus and 20 mg/kg per hour i.v. for 24 h) in a blinded, randomized fashion. All piglets were acidotic and in cardiogenic shock after hypoxia. Treating the piglets with NAC significantly increased both renal blood flow and oxygen delivery throughout the reoxygenation period. N-acetyl-l-cysteine treatment also improved the renal function with the attenuation of elevated urinary N-acetyl-β-d-glucosaminidase activity and plasma creatinine concentration observed in H/R controls (both P < 0.05). The tissue levels of lipid hydroperoxides and caspase 3 in the kidney of NAC-treated animals were significantly lower than those of H/R controls. Conclusively, postresuscitation administration of NAC elicits a prolonged beneficial effect in improving renal functional recovery and reducing oxidative stress in newborn piglets with H/R insults for 48 h.

Beneficial effects of N-acetyl cysteine on pancreas and kidney following experimental pancreatic ischemia-reperfusion in rats

OBJECTIVE

To evaluate the protective effects of N-acetyl cysteine on the pancreas and kidney after pancreatic ischemia reperfusion injury in a rat model.

METHODS AND MATERIALS

Pancreatic ischemia reperfusion was performed in Wistar rats for 1 hour. Revascularization was achieved followed by 4 h of reperfusion. A total of 24 animals were divided into four groups: Group 1: sham; Group 2: pancreatic ischemia reperfusion without treatment; Group 3: pancreatic ischemia reperfusion plus N-acetyl cysteine intravenously; and Group 4: pancreatic ischemia reperfusion plus N-acetyl cysteine per os. Blood and tissue samples were collected after reperfusion.

RESULTS

There were significant differences in amylase levels between Group 1 (6.11+/-0.55) and Group 2 (10.30+/-0.50) [p=0.0002] as well as between Group 2 (10.30+/-0.50) and Group 4 (7.82+/-0.38) [p=0.003]; creatinine levels between Group 1 (0.52 +/- 0.07) and Group 2 (0.77+/-0.18) [p=0.035] as well as between Group 2 (0.77+/-0.18) and Group 3 (0.48+/-0.13) [p=0.012]; and pancreatic tissue thiobarbituric acid reactive substance levels between Group 1 (1.27+/-0.96) and Group 2 (2.60+/-3.01) [p=0.026] as well as between Group 2 (2.60+/-3.01) and Group 4 (0.52+/-0.56) [p=0.002]. A decrease in pancreatic tissue GST-alpha3 gene expression was observed in Group 2 in comparison to Group 1 (p =0.006), and an increase was observed in Groups 3 and 4 when compared to Group 2 (p= 0.025 and p=0.010, respectively).

CONCLUSION

This study provides evidence that N-acetyl cysteine has a beneficial effect on pancreatic ischemia reperfusion injury and renal function in a rat model.

Sodium bicarbonate plus N-acetylcysteine prophylaxis: a meta-analysis

OBJECTIVES

We sought to conduct a meta-analysis to compare N-acetylcysteine (NAC) in combination with sodium bicarbonate (NaHCO(3)) for the prevention of contrast-induced acute kidney injury (AKI).

BACKGROUND

Contrast-induced AKI is a serious consequence of cardiac catheterizations and percutaneous coronary interventions (PCI). Despite recent supporting evidence for combination therapy, not enough has been done to prevent the occurrence of contrast-induced AKI prophylactically.

METHODS

Published randomized controlled trial data were collected from OVID/PubMed, Web of Science, and conference abstracts. The outcome of interest was contrast-induced AKI, defined as a >or=25% or >or=0.5 mg/dl increase in serum creatinine from baseline. Secondary outcome was renal failure requiring dialysis.

RESULTS

Ten randomized controlled trials met our criteria. Combination treatment of NAC with intravenous NaHCO(3) reduced contrast-induced AKI by 35% (relative risk: 0.65; 95% confidence interval: 0.40 to 1.05). However, the combination of N-acetylcysteine plus NaHCO(3) did not significantly reduce renal failure requiring dialysis (relative risk: 0.47; 95% confidence interval: 0.16 to 1.41).

CONCLUSIONS

Combination prophylaxis with NAC and NaHCO(3) substantially reduced the occurrence of contrast-induced AKI overall but not dialysis-dependent renal failure. Combination prophylaxis should be incorporated for all high-risk patients (emergent cases or patients with chronic kidney disease) and should be strongly considered for all interventional radio-contrast procedures.

N-Acetylcysteine Antagonizes the Development But Does Not Reverse ACTH-Induced Hypertension in the Rat

We investigated the effect of antioxidant N-acetylcysteine (NAC) on adrenocorticotropic hormone (ACTH)-hypertension. Male Sprague-Dawley rats received NAC (10 mg/L) or water 4 days before ACTH/saline treatment for 13 days (prevention study). In a reversal study, NAC commenced on day 8 of ACTH/saline treatment and continued for 5 days. ACTH increased systolic blood pressure (SBP) in water drinking rats (111 +/- 1 to 131 +/- 3 mmHg, p < 0.001). In the prevention study, NAC + ACTH increased SBP (108 +/- 2 to 120 +/- 2 mmHg, p < 0.001) but less than ACTH alone (p' < 0.05). In the reversal study, NAC had no significant effect (132 +/- 4 to 124 +/- 3 mmHg, ns). Thus, NAC partially prevented but did not reverse ACTH-induced hypertension.

N-Acetylcysteine Infusion Improves Hepatic Perfusion in the Early Stages of Systemic Sclerosis

The aim of our study is to evaluate portal and hepatic hemodynamic changes after N-acetylcysteine infusion in patients with systemic sclerosis. In an open-label study 40 patients with Systemic Sclerosis (SSc) were treated with 15mg/kg/hour intravenous N-acetylcysteine for 5 consecutive hours in a single day. Hepatic flow volume, congestion index, portal flow volume, resistance index and pulse rate index were measured in each subject before and after infusion. In all patients mean hepatic flow volume (HFV) and mean portal flow volume (PFV) values after the five-hour infusion with NAC increased not significantly. In 22 selected patients with active capillaroscopic pattern, modified Rodnan Total Skin Score (mRTSS) <18 and mild-moderate score to vascular domain of disease severity scale (DSS), mean HFV increased significantly when compared with mean HFV of 18 SSc patients with late capillaroscopic pattern, mRTSS >18 and severe-end stage score to vascular domain of DSS. The results of our study demonstrate that NAC is able to increase HFV and total liver perfusion after a single infusion in SSc patients with low disease activity and severity scores.

Post-resuscitation NOS inhibition does not improve hemodynamic recovery of hypoxic newborn pigs

BACKGROUND

Significant improvement in myocardial recovery has been shown previously with interventions to decrease reactive oxygen species after ischemia/hypoxia. We investigated whether co-administration of N-acetylcysteine (NAC, a scavenger for reactive oxygen species) and N (G)-monomethyl-L: -arginine (L-NMMA, a non-selective nitric oxide synthase inhibitor) results in better hemodynamic recovery.

DESIGN

Controlled, block-randomized study.

SETTING

University research laboratory.

SUBJECT

Mixed breed piglets (1-4d, 1.6-2.4 kg).

INTERVENTIONS

Acutely instrumented piglets received normocapnic alveolar hypoxia (10-15% oxygen) for 2 h followed by reoxygenation with 100% oxygen (1 h) then 21% oxygen (3 h). After reoxygenation, hypoxic-reoxygenated piglets were given either saline (controls), NAC [30 mg/kg bolus + 20 mg/(kg h) infusion], NMMA [0.1 mg/kg bolus + 0.1 mg/(kg h) infusion] or NAC + L-NMMA via intravenous infusion in a blinded, randomized fashion (n = 8/group). Sham-operated piglets had no hypoxia-reoxygenation (n = 5).

MEASUREMENTS AND RESULTS

Both cardiac index and stroke volume of hypoxia-reoxygenation controls remained depressed during reoxygenation (vs. normoxic baseline, p < 0.05). Post-resuscitation treatment with L-NMMA alone did not improve systemic hemodynamic recovery, but caused pulmonary hypertension (vs. controls). In contrast, treating the piglets with either NAC or NAC + L-NMMA improved cardiac index and stroke volume, with no effect on heart rate and blood pressure (vs. controls). These treatments also decreased various oxidative stress markers in myocardial tissues (vs. controls). However, there was no significant difference between NAC- and NAC + L-NMMA groups in all examined parameters.

CONCLUSIONS

Post-resuscitation administration of NAC improved cardiac function and reduced oxidative stress in newborn pigs with hypoxia-reoxygenation insult. Low-dose, non-selective inhibitor of nitric oxide synthase activity did not provide any further beneficial effect.

N-Acetylcysteine prevents but does not reverse dexamethasone-induced hypertension

1. We have shown previously that N-acetylcysteine (NAC) prevents the increase in blood pressure induced by adrenocorticotropin treatment. The present study investigated the effect of NAC on dexamethasone (Dex)-induced hypertension. 2. Male Sprague-Dawley rats were randomly divided into six groups (n = 10 in each). In a prevention study, NAC (10 g/L in the drinking water) was given for 4 days prior to and 11 days during concurrent treatment with saline (0.1 mL/rat per day) or with Dex (10 mg/rat per day). In a reversal study, daily injections of Dex or saline began 8 days before NAC and cotreatment continued for 5 days. Systolic blood pressure (SBP) was measured on alternate days using a tail-cuff system. 3. Dexamethasone significantly increased SBP from 113 +/- 4 to 139 +/- 6 mmHg (n = 10; P < 0.01). N-Acetylcysteine alone had no effect on SBP. In NAC + Dex-treated rats, SBP was significantly lower than that of Dex-treated rats (P cent < 0.01). In fully established Dex-hypertension NAC was ineffective and SBP remained high. 4. Both Dex and NAC treatments decreased bodyweight gain. N-Acetylcysteine reduced food and water consumption. Dexamethasone reduced thymus weight (P cent < 0.01) but NAC treatment did not alter this marker of glucocorticoid activity. 5. Dexamethasone tended to decrease plasma NO(x), whereas NAC restored plasma NO(x) concentrations to control levels. N-Acetylcysteine had no effect on Dex-induced increased plasma F(2)-isoprostane concentrations. 6. In conclusion, NAC partially prevented, but did not reverse, Dex-induced hypertension.

Prevention of radiocontrast medium-induced nephropathy using short-term high-dose simvastatin in patients with renal insufficiency undergoing coronary angiography (PROMISS) trial--a randomized controlled study

BACKGROUND

Contrast media cause oxidative stress, which has been suggested as one possible mechanism responsible for contrast-induced nephropathy. Statins appear to have pleiotropic effects, including antioxidant properties. We investigated to determine whether simvastatin pretreatment reduces the risk of contrast-induced nephropathy in a high-risk population of patients with renal insufficiency undergoing coronary angiography.

METHODS

We conducted a prospective, randomized, double-blind, placebo-controlled, 2-center trial, involving 247 consecutive patients with chronic renal insufficiency (calculated creatinine clearance < or = 60 mL/min and/or serum creatinine > or = 1.1 mg/dL) undergoing coronary angiography. Patients were randomized to simvastatin (n = 124; 160 mg total, 40 mg orally every 12 hours starting the evening before and ending the morning after the procedure) or placebo (n = 123). All patients received pre - and postprocedure hydration. The iso-osmolar contrast agent iodixanol was used for coronary angiography in all patients.

RESULTS

There was no difference between simvastatin and placebo in mean peak increase in serum creatinine measured within 48 hours after coronary angiography, the primary study end point (0.002 +/- 0.164 vs 0.017 +/- 0.230 mg/mL respectively, P = .559). The incidence of contrast-induced nephropathy, a secondary end point defined as increase of either > or = 25% or > or = 0.5 mg/dL in serum creatinine, was 2.5% in simvastatin-treated patients (3/118) and 3.4% in placebo-treated patients (4/118), a nonsignificant difference (P = 1.00). There were also no differences between the 2 groups in length of hospital stay or 1- and 6-month clinical outcomes.

CONCLUSIONS

Simvastatin pretreatment for short-term at high dose do not prevent renal function deterioration after administration of contrast medium in patients with baseline renal insufficiency undergoing coronary angiography.

N-acetyl cysteine supplementation prevents impairment of spatial working memory functions in rats following exposure to hypobaric hypoxia

Exposure to high altitude (HA), especially extreme altitude, is associated with impairment of cognitive functions including memory and increased oxidative stress. However, the underlying mechanisms involved are not well understood. It is hypothesized that HA induced oxidative stress may be one of the factors underlying hypoxia induced memory impairment. The aim of the present study was to investigate the effect of hypobaric hypoxia (HH) on spatial working and reference memory functions, oxidative stress markers in rats and effect of supplementation of N-acetyl cysteine (NAC). The rats were divided into four groups. Group I served as normoxic (n=6), Group II served as hypoxic (n=6), Group III as hypoxia group treated with NAC (n=6) and Group IV served as normoxic group treated with NAC (n=6). Group II & III were exposed to HH for 3 days equivalent to 6100 m and received oral NAC supplementation (750 mg/kg) daily. Rats from all the groups were trained in Morris Water Maze (MWM) task for 8 consecutive days. Spatial working and reference memory were tested immediately after the termination of HH and then the rats were sacrificed for estimation of oxidative stress markers in hippocampus. Rats displayed significant deficits in spatial working memory, and increased oxidative stress along with decrease in antioxidant status on hypoxic exposure. Supplementation with NAC in hypoxia-exposed group improved spatial memory performance, and decreased oxidative stress. These findings indicate that hypoxic exposure is associated with increased oxidative stress, which may have caused memory deficit in rats exposed to simulated HA.

Comparison of usefulness of sodium bicarbonate versus sodium chloride to prevent contrast-induced nephropathy in patients undergoing an emergent coronary procedure

In the case of an emergency coronary procedure where the risk of contrast-induced nephropathy is especially high, there are few reliable methods to attenuate renal injury. We examined the efficacy of sodium bicarbonate for the prevention of contrast-induced nephropathy in patients undergoing an emergency coronary procedure. We enrolled 59 patients who were scheduled to undergo an emergency coronary angiography or intervention. These patients were randomized to receive a 154-mEq/L infusion of sodium bicarbonate (n = 30) or sodium chloride (n = 29), as a bolus of 3 ml/kg/hour for 1 hour before the administration of contrast, followed by an infusion of 1 ml/kg/hour for 6 hours during and after the procedure. In the sodium bicarbonate group, serum creatinine concentration remained unchanged within 2 days of contrast administration (1.31 +/- 0.52 to 1.31 +/- 0.59 mg/dl), whereas it increased in the sodium chloride group (1.32 +/- 0.65 to 1.52 +/- 0.92 mg/dl, p = 0.01). The incidence of contrast-induced nephropathy (an increase >0.5 mg/dl or >25% in serum creatinine concentration within 2 days of contrast) was significantly lower in the sodium bicarbonate group than in the sodium chloride group (7% vs 35%, p = 0.01, risk ratio 0.19, 95% confidence interval 0.046 to 0.80). In conclusion, hydration with sodium bicarbonate is more effective than with sodium chloride for the prevention of contrast-induced nephropathy in patients undergoing an emergency coronary procedure.

Effect of N-Acetylcysteine on Endothelial Dysfunction in Dialysis Patients

BACKGROUND/AIMS

Patients with K/DOQI stage 5 chronic kidney disease (CKD) have higher incidence of cardiovascular events due to the oxidative stress and endothelial dysfunction (ED). The aim of this study is to evaluate the effects of N-acetylcysteine (NAC), which might prevent cardiovascular events by improving oxidative stress on endothelial cells in patients with CKD.

METHODS

Thirty uremic patients (age 40 +/- 12 years, 6 males) on hemodialysis (HD) were evaluated for ED by using high-resolution Doppler ultrasound of brachial artery before and after 6 weeks of oral NAC (2 x 600 mg) medication. Also, 13 healthy controls (35 +/- 9 years, 5 males) were included in the study. Reactive hyperemia following 5 min forearm ischemia was accepted as endothelium-dependent vasodilatation (flow-mediated dilatation; FMD) and compared to endothelium-independent vasodilatation in response to sublingual glyceril trinitrate (GTN).

RESULTS

Patients on HD had lower DeltaFMD (0.28 +/- 0.17 vs. 0.41 +/- 0.11, p < 0.05) and FMD% (7.5 +/- 5.05 vs. 11.33 +/- 2.95, p < 0.05) than the controls. Baseline DeltaGTN and GTN% were similar in two groups. NAC treatment significantly increased the DeltaFMD (0.41 +/- 0.11, p < 0.001 vs. baseline) and FMD% (10.59 +/- 3.22, p < 0.01 vs. baseline) of patients on HD, while it had no effect on DeltaGTN and GTN%.

CONCLUSION

These results suggest that NAC treatment could improve the ED by preventing the reduction of FMD in patients on HD.

Strategies to reduce the risk of contrast nephropathy: an evidence-based approach

PURPOSE OF REVIEW

Contrast nephropathy is a common complication associated with angiographic procedures that carries significant morbidity and mortality. Recent clinical trials of prophylactic strategies have reported contradictory results. This review presents recent insights into the pathophysiology of contrast nephropathy and reviews trial results in this context.

RECENT FINDINGS

A prediction rule has been developed to better identify patients at risk of developing contrast nephropathy. Factors other than osmolality play a significant role in the pathogenesis of contrast nephropathy, at least for agents with osmolalities of 800 mOsm/kg or less. New randomized trial data do not support a role for N-acetylcysteine in contrast nephropathy prophylaxis and there is additional evidence that fenoldopam is ineffective. Pooled analyses of theophylline prophylaxis trials are inconclusive. Theoretical and clinical data suggest that ascorbic acid may be renoprotective, but this requires further study.

SUMMARY

The overall incidence of contrast nephropathy remains low. Available evidence supports the use of hydration and low volumes of iso-osmolar or low-osmolar contrast in patients at risk of developing contrast nephropathy. Heterogeneity has affected interpretability of interventional trials of N-acetylcysteine or theophylline prophylaxis strategies. Future clinical trials must identify and target moderate-risk to high-risk patients and ensure that proven therapies are included in trial protocols.

Systematic review of the impact of N-acetylcysteine on contrast nephropathy

BACKGROUND

The efficacy of N-acetylcysteine (NAC) for preventing contrast nephropathy is uncertain. We performed a systematic review and meta-analysis to assess the efficacy of NAC for preventing contrast nephropathy after administration of intravenous contrast media.

METHODS

Data were obtained from searching MEDLINE (1969-2003) and EMBASE (1988-2003), Cochrane Controlled Clinical Trial Registry (2002, Volume 3), and conference proceedings. We considered all randomized studies that compared changes in renal function between groups that received and did not receive NAC. Studies in which the control group also received active therapy were excluded, although co-intervention directed at both groups was permitted. Two reviewers independently extracted quantitative and qualitative data. Disagreements were resolved by consensus with the aid of a third party.

RESULTS

Fifteen studies with a total of 1776 patients satisfied inclusion and exclusion criteria. Contrast nephropathy was typically defined by an increase in serum creatinine of 0.5 mg/dL within 24 to 48 hours of contrast administration. The pooled random effect relative risk was 0.65 (0.43-1.00, P= 0.049), indicating that NAC significantly reduced the incidence of contrast nephropathy. However, the effect of NAC was not statistically significant in several prespecified subgroup analyses, and the results were not robust to the addition of hypothetical new or unidentified randomized trials. There was evidence of significant heterogeneity in NAC effect across studies (Q = 26.3, P= 0.02). Random effects meta-regression did not implicate identified differences in participant or study characteristics as responsible for the observed heterogeneity.

CONCLUSION

NAC may reduce the incidence of acutely increased serum creatinine after administration of intravenous contrast, but this finding was of borderline statistical significance, and there was significant heterogeneity between trials. Before NAC becomes the standard of care for all patients receiving intravenous contrast, new randomized trials evaluating its effect on clinically relevant outcomes are required.

Differential modulation of citrate synthesis and release by fatty acids in perfused working rat hearts

The objective of this study was to test the effect of increasing fatty acid concentrations on substrate fluxes through pathways leading to citrate synthesis and release in the heart. This was accomplished using semirecirculating work-performing rat hearts perfused with substrate mixtures mimicking the in situ milieu (5.5 mM glucose, 8 nM insulin, 1 mM lactate, 0.2 mM pyruvate, and 0.4 mM oleate-albumin) and 13C methods. Raising the fatty acid concentration from 0.4 to 1 mM with long-chain oleate or medium-chain octanoate resulted in a lowering ( approximately 20%) of cardiac output and efficiency with unaltered O2 consumption. At the metabolic level, beyond the expected effects of high fatty acid levels on the contribution of pyruvate decarboxylation (reduced >3-fold) and beta-oxidation (enhanced approximately 3-fold) to citrate synthesis, there was also a 2.4-fold lowering of anaplerotic pyruvate carboxylation. Despite the dual inhibitory effect of high fatty acids on pyruvate decarboxylation and carboxylation, tissue citrate levels were twofold higher, but citrate release rates remained unchanged at 11-14 nmol/min, representing <0.5% of citric acid cycle flux. A similar trend was observed for most metabolic parameters after oleate or octanoate addition. Together, these results emphasize a differential modulation of anaplerotic pyruvate carboxylation and citrate release in the heart by fatty acids. We interpret the lack of effects of high fatty acid concentrations on citrate release rates as suggesting that, under physiological conditions, this process is maximal, probably limited by the activity of its mitochondrial or plasma membrane transporter. Limited citrate release at high fatty acid concentrations may have important consequences for the heart's fuel metabolism and function.

The antioxidant acetylcysteine reduces cardiovascular events in patients with end-stage renal failure: a randomized, controlled trial

BACKGROUND

Patients with end-stage renal failure have increased oxidative stress and show elevated cardiovascular mortality. Whether increased cardiovascular events can be prevented by the administration of antioxidants is unknown.

METHODS AND RESULTS

We evaluated the effects of acetylcysteine, a thiol-containing antioxidant, on cardiovascular events in patients undergoing hemodialysis. A prospective, randomized, placebo-controlled trial was conducted between October 1, 1999, and September 30, 2001, in 134 patients (76 male and 58 female) with a mean age of 62+/-16 years (mean+/-SD) who had been undergoing maintenance hemodialysis for a minimum of 3 months 3 times weekly in an ambulatory center. Median (range) follow-up was 14.5 (1 to 24) months. Patients were randomly assigned either to receive acetylcysteine (600 mg BID) or placebo. The primary end point was a composite variable consisting of cardiac events including fatal and nonfatal myocardial infarction, cardiovascular disease death, need for coronary angioplasty or coronary bypass surgery, ischemic stroke, peripheral vascular disease with amputation, or need for angioplasty. Secondary end points included each of the component outcomes, total mortality, and cardiovascular mortality. A total of 18 (28%) of the 64 hemodialysis patients assigned to acetylcysteine group and 33 (47%) of the 70 hemodialysis patients assigned to control group had a primary end point (relative risk, 0.60 [95% CI, 0.38 to 0.95], P=0.03). No significant differences in secondary end points or total mortality were detected.

CONCLUSIONS

In hemodialysis patients, treatment with acetylcysteine (600 mg BID) reduces composite cardiovascular end points.

Quantitative gas chromatographic-mass spectrometric assay of 4-hydroxynonenal bound to thiol proteins in ischemic/reperfused rat hearts

Increasing evidence indicates that protein-aldehyde adducts involving mostly 4-hydroxynonenal could be causally involved in both pathophysiological and adaptive events following an oxidative stress insult such as ischemia/reperfusion. The goal of this study was to assess if isotope dilution chromatography-mass spectrometry can be used to quantitate changes in the cardiac levels of 4-hydroxynonenal and 1,4-dihydroxynonene, one of its major metabolites, bound to thiol proteins during ischemia/reperfusion. For this purpose, we modified a previously published method to include treatment with Raney Nickel, which specifically cleaves thioether linkages. Our study model was the isolated Langendorff-perfused rat heart subjected to various ischemia/reperfusion protocols. Hearts perfused under normoxia contained small amounts of protein-bound 4-hydroxynonenal and 1,4-dihydroxynonene (1.38 +/- 0.29 and 2.69 +/- 0.17 nmol/g wet weight, respectively). The accumulation of these adducts after global ischemia depended on the severity of the ischemic insult up to a plateau and was not exacerbated by reperfusion. In conclusion, our method allows the quantification of time-dependent changes in 4-hydroxynonenal and 1,4-dihydroxynonene bound to proteins via thioether linkage in ischemic/reperfused heart tissues. The presence of protein-bound 1,4-dihydroxynonene in heart tissues suggests that this organ can detoxify protein-bound 4-hydroxynonenal.

Reverse flux through cardiac NADP(+)-isocitrate dehydrogenase under normoxia and ischemia

Little is known about the role of mitochondrial NADP(+)-isocitrate dehydrogenase (NADP(+)-ICDH) in the heart, where this enzyme shows its highest expression and activity. We tested the hypothesis that in the heart, NADP(+)-ICDH operates in the reverse direction of the citric acid cycle (CAC) and thereby may contribute to the fine regulation of CAC activity (Sazanov and Jackson, FEBS Lett 344: 109-116, 1994). We documented a reverse flux through this enzyme in rat hearts perfused with the medium-chain fatty acid octanoate using [U-(13)C(5)]glutamate and mass isotopomer analysis of tissue citrate (Comte et al., J Biol Chem 272: 26117-26124, 1997). In this study, we assessed the significance of our previous finding by perfusing hearts with long-chain fatty acids and tested the effects of changes in O(2) supply. We showed that under all of these conditions citrate was enriched in an isotopomer containing five (13)C atoms. This isotopomer can only be explained by substrate flux through reversal of the NADP(+)-ICDH reaction, which is evaluated at 3-7% of flux through citrate synthase. Small variations in reversal fluxes induced by low-flow ischemia that mimicked hibernation occurred despite major changes in contractile function and O(2) consumption of the heart as well as citrate and succinate release rates and tissue levels. Our data show a reverse flux through NADP(+)-ICDH and support its hypothesized role in the fine regulation of CAC activity in the normoxic and O(2)-deprived heart.

Update on cardiovascular disease in post-menopausal women

Cardiovascular disease (CVD), and in particular coronary artery heart disease (CAHD), is the leading cause of morbidity and mortality in women. Until recently, most of our knowledge about the pathophysiology of CVD in women - and, subsequently, management guidelines - were based on studies conducted mostly in men. While similar mechanisms operate to induce CVD in women and men, gender-related differences exist in the anatomy and physiology of the myocardium, and sex hormones modify the course of disease in women. Women, more than men, have their initial manifestation of CAHD as angina pectoris; are likely to be referred for diagnostic tests at a more advanced stage of disease, and are less likely than men to have corrective invasive procedures. The overall morbidity and mortality following the initial ischaemic heart event is worse in women, and the case fatality rate is greater in women than in men. Also, the relative impact of impaired vasoreactivity of the coronary artery, increased viscosity of the blood and dysregulation of automaticity and arrhythmia, is greater in women than in men. The most effective means of decreasing the impact of CVD on women's health is by an active approach from childhood to proper principles of healthcare in order to modify the contribution of specific risk factors. The latter include obesity, abnormal plasma lipid profile, hypertension, diabetes mellitus, cigarette smoking, sedentary lifestyle, increased blood viscosity, augmented platelet aggregability, stress and autonomic imbalance. The use of lipid-lowering drugs has not been adequately studied in women but reports from studies conducted mostly in men do predict an advantage also to women. Oestrogen deficiency after spontaneous or medically induced menopause is an important risk factor for CVD and CAHD. Observational and mechanistic data suggest a role for oestrogen replacement after menopause for primary, and possibly secondary, prevention of CVD. However, two recent prospective trials suggest that treatment de novo with hormone replacement of older post-menopausal women after an acute coronary event may not confer cardiovascular protection and may increase the risk of thromboembolic disease. Results of ongoing long-term studies may determine the beneficial role of hormone replacement versus potential risks involved with this treatment.

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.

Reactive oxygen species contribute to contractile dysfunction following rapid ventricular pacing in dogs

BACKGROUND

Ventricular tachyarrhythmias may produce subsequent myocardial dysfunction through the formation of oxygen-derived free radicals. We tested the hypothesis that the antioxidant N-acetylcysteine enhances recovery of contractile function after rapid ventricular pacing.

METHODS

Barbiturate-anesthetized dogs were instrumented for measurement of systemic and coronary hemodynamics and subendocardial segment shortening (%SS). All dogs were subjected to 3 h of rapid ventricular pacing (230 beats/min) followed by a 2 h recovery period. In three groups (n=8 each), dogs received intravenous 0.9% saline or N-acetylcysteine (50 or 150 mg/kg over 60 min) in a random manner before pacing.

RESULTS

N-acetylcysteine did not affect systemic and coronary hemodynamics or alter regional myocardial contractility. Rapid ventricular pacing significantly (P<0.05) increased rate-pressure product and left ventricular end-diastolic pressure and decreased +dP/dt(max). Rapid ventricular pacing produced equivalent degrees of contractile dysfunction in dogs receiving saline or N-acetylcysteine (e.g. %SS of 14.7+/-1.8 to -3.8+/-2.7% before and during pacing in saline-pretreated dogs). Dogs receiving the 150 mg/kg dose of N-acetylcysteine demonstrated greater recovery of contractile function than those pretreated with saline or the 50 mg/kg dose (e.g. %SS of 12.3+/-1.7% compared to 7.0+/-2.0% 2 h after pacing in dogs receiving saline). No differences in systemic and coronary hemodynamics were observed between groups during recovery from pacing.

CONCLUSIONS

The results indicate that the N-acetylcysteine enhances recovery of contractile function after rapid ventricular pacing independent of alterations in systemic and coronary hemodynamics and imply that reactive oxygen species are an important component of the contractile dysfunction following rapid pacing in vivo.

Acetylcysteine for radiocontrast nephropathy

Radiocontrast nephropathy may in part be mediated by generation of reactive oxygen species causing direct toxic damage to renal tubular epithelial cell and renal medullary ischemia. Data from experimental studies indicated that antioxidants, eg, acetylcysteine, may prevent radiocontrast-induced nephropathy. Recently, one prospective, randomized, placebo-controlled study in patients with moderate renal insufficiency confirmed that the prophylactic oral administration of acetylcysteine at a dose of 600 mg twice daily along with hydration prevents the reduction in renal function by a nonionic, low-osmolality radiocontrast agent.

Electronegative LDL from normolipemic subjects induces IL-8 and monocyte chemotactic protein secretion by human endothelial cells

The presence in plasma of an electronegative LDL subfraction [LDL(-)] cytotoxic for endothelial cells (ECs) has been reported. We studied the effect of LDL(-) on the release by ECs of molecules implicated in leukocyte recruitment [interleukin-8 (IL-8) and monocyte chemotactic protein-1 (MCP-1)] and in the plasminogen activator inhibitor-1 (PAI-1). LDL(-), isolated by anion-exchange chromatography, differed from nonelectronegative LDL [LDL(+)] in its higher triglyceride, nonesterified fatty acid, apoprotein E and apoprotein C-III, and sialic acid contents. No evidence of extensive oxidation was found in LDL(-); its antioxidant and thiobarbituric acid-reactive substances contents were similar to those of LDL(+). However, conjugated dienes were increased in LDL(-), which suggests that mild oxidation might affect these particles. LDL(-) increased, in a concentration-dependent manner, the release of IL-8 and MCP-1 by ECs and was a stronger inductor of both chemokines than oxidized LDL (oxLDL) or LDL(+). PAI-1 release increased slightly in ECs incubated with both LDL(-) and oxLDL but not with LDL(+). However, no cytotoxic effects of LDL(-) were observed on ECs. Actinomycin D inhibited the release of IL-8 and MCP-1 induced by LDL(-) and oxLDL by up to 80%, indicating that their production is mediated by protein synthesis. Incubation of ECs with N:-acetyl cysteine inhibited production of IL-8 and MCP-1 induced by LDL(-) and oxLDL by >50%. The free radical scavenger butylated hydroxytoluene slightly inhibited the effect of oxLDL but did not modify the effect of LDL(-). An antagonist (BN-50730) of the platelet-activating factor receptor inhibited production of both chemokines by LDL(-) and oxLDL in a concentration-dependent manner. Our results indicate that LDL(-) shows proinflammatory activity on ECs and may contribute to early atherosclerotic events.

Citrate release by perfused rat hearts: a window on mitochondrial cataplerosis

Cytosolic citrate is proposed to play a crucial role in substrate fuel selection in the heart. However, little is known about factors regulating the transfer of citrate from the mitochondria, where it is synthesized, to the cytosol. Further to our observation that rat hearts perfused under normoxia release citrate whose (13)C labeling pattern reflects that of mitochondrial citrate (B. Comte, G. Vincent, B. Bouchard, and C. Des Rosiers. J. Biol. Chem. 272: 26117-26124, 1997), we report here data indicating that this citrate release is a specific process reflecting the mitochondrial efflux of citrate, a process referred to as cataplerosis. Indeed, measured rates of citrate release, which vary between 2 and 21 nmol/min, are modulated by the nature and concentration of exogenous substrates feeding acetyl-CoA (fatty acid) and oxaloacetate (lactate plus pyruvate) for the mitochondrial citrate synthase reaction. Such release rates that represent at most 2% of the citric acid cycle flux are in agreement with the activity of the mitochondrial tricarboxylate transporter whose participation is also substantiated by 1) parallel variations in citrate release rates and tissue levels of citrate plus malate, the antiporter, and 2) a lowering of the citrate release rate by 1,2, 3-benzenetricarboxylic acid, a specific inhibitor of the transporter. Taken together, the results from the present study indicate that citrate cataplerosis is modulated by substrate supply, in agreement with the role of cytosolic citrate in fuel partitioning, and occurs, at least in part, through the mitochondrial tricarboxylate transporter.

Hyperbaric oxygen increases plasma exudation in rat trachea: involvement of nitric oxide

This study investigates the microvascular permeability changes in tracheal tissue of rats exposed to hyperbaric oxygen (HBO). Rats, following exposure to HBO or ambient air (control animals) for 1.5, 3 and 6 h, were prepared for recording of nitric oxide exhaled (FENO) in air using a chemiluminescence analyser. The level of FENO was not statistically different in the two groups. Plasma exudation, evaluated by measuring the leakage of Evans blue (EB) dye into the tracheal tissue, was significantly elevated (48, 86 and 105% at 1.5, 3 and 6 h, respectively) in HBO-treated rats. Plasma exudation in the trachea of control rats was significantly increased (42%, P<0.05) by NG-nitro-L-arginine methyl ester (L-NAME), whereas it was significantly reduced (31%, P<0.05) in rats exposed to HBO for 3 h. N-acetylcysteine (NAC) and flunisolide significantly prevented the increase in plasma leakage in HBO-treated rats. In contrast, indomethacin was devoid of anti-exudative activity in these experiments. Western immunoblot showed a significant increase in the level of inducible nitric oxide synthase (iNOS) protein in the tracheal homogenates of HBO-treated rats, as compared to basal levels. These results indicate that nitric oxide (NO) is involved in the maintenance of microvascular permeability in tracheal tissue of rats. The protective effect observed with the steroid seems to support this hypothesis. Furthermore, the beneficial action of NAC underlines that reactive oxygen species participate in the microvascular permeability changes observed in tracheal tissue of rats exposed to HBO.

Nitric oxide and N-acetylcysteine inhibit the activation of mitogen-activated protein kinases by angiotensin II in rat cardiac fibroblasts

Angiotensin II acts on the cardiac fibroblast to produce a mitogenic response. Nitric oxide and N-acetylcysteine have been used to determine if oxidative stress influenced the effects of angiotensin II on the cardiac fibroblast. Angiotensin II activated the mitogen-activated protein kinases designated extracellular signal-regulated kinases within 5 min by interacting with the AT1 receptor. This activation was completely independent of protein kinase C and was inhibited when farnesylation was blocked, implicating Ras involvement. Pretreatment of cardiac fibroblasts with either N-acetylcysteine for 8 h or nitric oxide for 10 min suppressed this activation by angiotensin II in a dose-dependent manner. However, when both agents were added, inhibition was essentially complete. This combined effect of N-acetylcysteine and nitric oxide to block ERKs activation also was found if the activity was stimulated by either another growth factor (platelet-derived growth factor) or by the addition of phorbol ester, suggesting the effect was not limited to the receptor site alone. The results are consistent with the hypothesis that hormonal activation of mitogenic steps such as ERKs is influenced by increased oxidative stress, which is reduced by the combined effects of N-acetylcysteine and nitric oxide.

Temporal and kinetic determinants of the inhibition of LDL oxidation by N-acetylcysteine (NAC)

We investigated the ability of NAC to inhibit in vitro LDL oxidation, and the effects of the timing of NAC addition, repeated additions of NAC, and the presence of preoxidized LDL, on the oxidation reaction. NAC inhibited in vitro LDL oxidation induced by copper sulfate, 2,2'-azobis(2-amidinopropane) dihydrochloride, and UV light, and protected LDL against depletion of antioxidant vitamins. Glutathione was similarly effective against copper-mediated LDL oxidation. NAC's effectiveness was inversely related to the timing of its addition. Sequential NAC additions prolonged the lag phase more effectively than initial addition of the same total dose. NAC reduced CD formation during the oxidation of native LDL by oxidized LDL. NAC's effectiveness as an inhibitor of in vitro LDL oxidation is dependent on the temporal sequence of the oxidation reaction, sequential additions, and the presence of previously oxidized LDL.

Mechanism of copper-catalyzed oxidation of glutathione

The mechanism of copper-catalyzed glutathione oxidation was investigated using oxygen consumption, thiol depletion, spectroscopy and hydroxyl radical detection. The mechanism of oxidation has kinetics which appear biphasic. During the first reaction phase a stoichiometric amount of oxygen is consumed (1 mole oxygen per 4 moles thiol) with minimal .OH production. In the second reaction phase, additional (excess) oxygen is consumed at an increased rate and with significant hydrogen peroxide and .OH production. The kinetic and spectroscopic data suggest that copper forms a catalytic complex with glutathione (1 mole copper per 2 moles glutathione). Our proposed reaction mechanism assumes two parallel processes (superoxide-dependent and peroxide-dependent) for the first reaction phase and superoxide-independent for the second phase. Our current results indicate that glutathione, usually considered as an antioxidant, can act as prooxidant at physiological conditions and therefore can participate in cellular radical damage.

A 13C mass isotopomer study of anaplerotic pyruvate carboxylation in perfused rat hearts

Anaplerotic pyruvate carboxylation was examined in hearts perfused with physiological concentrations of glucose, [U-13C3]lactate, and [U-13C3]pyruvate. Also, a fatty acid, [1-13C]octanoate, or ketone bodies were added at concentrations providing acetyl-CoA at a rate resulting in either low or substantial pyruvate decarboxylation. Relative contributions of pyruvate and fatty acids to citrate synthesis were determined from the 13C labeling pattern of effluent citrate by gas chromatography-mass spectrometry (see companion article, Comte, B., Vincent, G., Bouchard, B., and Des Rosiers, C. (1997) J. Biol. Chem. 272, 26117-26124). Precision on flux measurements of anaplerotic pyruvate carboxylation depended on the mix of substrates supplied to the heart. Anaplerotic fluxes were precisely determined under conditions where acetyl-CoA was predominantly supplied by beta-oxidation, as it occurred with 0.2 or 1 mM octanoate. Then, anaplerotic pyruvate carboxylation provided 3-8% of the OAA moiety of citrate and was modulated by concentrations of lactate and pyruvate in the physiological range. Also, the contribution of pyruvate to citrate formation through carboxylation was equal to or greater than through decarboxylation. Furthermore, 13C labeling data on tissue citric acid cycle intermediates and pyruvate suggest that (i) anaplerosis occurs also at succinate and (ii) cataplerotic malate decarboxylation is low. Rather, the presence of citrate in the effluent perfusate of hearts perfused with physiological concentrations of glucose, lactate, and pyruvate and concentrations of octanoate leading to maximal oxidative rates suggests a cataplerotic citrate efflux from mitochondria to cytosol. Taken altogether, our data raise the possibility of a link between pyruvate carboxylation and mitochondrial citrate efflux. In view of the proposed feedback regulation of glycolysis by cytosolic citrate, such a link would support a role of anaplerosis and cataplerosis in metabolic signal transmission between mitochondria and cytosol in the normoxic heart.

Probing the origin of acetyl-CoA and oxaloacetate entering the citric acid cycle from the 13C labeling of citrate released by perfused rat hearts

We present a strategy for simultaneous assessment of the relative contributions of anaplerotic pyruvate carboxylation, pyruvate decarboxylation, and fatty acid oxidation to citrate formation in the perfused rat heart. This requires perfusing with a mix of 13C-substrates and determining the 13C labeling pattern of a single metabolite, citrate, by gas chromatography-mass spectrometry. The mass isotopomer distributions of the oxaloacetate and acetyl moieties of citrate allow calculation of the flux ratios: (pyruvate carboxylation)/(pyruvate decarboxylation), (pyruvate carboxylation)/(citrate synthesis), (pyruvate decarboxylation)/(citrate synthesis) (pyruvate carboxylation)/(fatty acid oxidation), and (pyruvate decarboxylation)/(fatty acid oxidation). Calculations, based on precursor-product relationship, are independent of pool size. The utility of our method was demonstrated for hearts perfused under normoxia with [U-13C3](lactate + pyruvate) and [1-13C]octanoate under steady-state conditions. Under these conditions, effluent and tissue citrate were similarly enriched in all 13C mass isotopomers. The use of effluent citrate instead of tissue citrate allows probing substrate fluxes through the various reactions non-invasively in the intact heart. The methodology should also be applicable to hearts perfused with other 13C-substrates, such as 1-13C-labeled long chain fatty acid, and under various conditions, provided that assumptions on which equations are developed are valid.

Hyperbaric oxygen worsens myocardial low flow ischemia-reperfusion injury in isolated rat heart

In these experiments rats were exposed to hyperbaric oxygen (100% oxygen; 2.5 atmospheres absolute pressure) for 1, 3 or 6 h. At the end of these periods the hearts were removed and subjected to low flow ischemia (perfusion rate from 12 ml/min to 2 ml/min for 40 min) and reperfusion. Hearts excised from control rats were subjected to the same procedure of ischemia and reperfusion. The data obtained from these experiments clearly indicate that the ischemic picture observed in control hearts is worsened in hearts obtained from hyperbaric oxygen-exposed animals. In fact, after ventricular standstill of the ischemic phase, the left ventricular end-diastolic pressure increased significantly and proportionally according to the time of hyperbaric oxygen exposure. The vasopressor activity of angiotensin II on coronary perfusion pressure was significantly changed, as compared to that in the control preparation: these alterations, well correlated to the time of hyperbaric oxygen exposure, seem to suggest impairment of the vascular endothelium-dependent relaxant function. Furthermore N-acetylcysteine and defibrotide, given orally to the rats before hyperbaric oxygen exposure, prevented the aggravation of the ischemic damage induced in ex vivo hearts.

Instantaneous analysis of aldehydes in biological fluids using a spray interface coupled to a mass spectrometer

A new interface coupled to a mass spectrometer was developed for the direct analysis of volatile organic compounds from small volumes of aqueous samples, including blood or tissue homogenates (St-Germain et al. 1995, Anal. Chem. 67:4536-4541). The greatest advantages of our system are minimal sample treatment, an instantaneous response time coupled with detection limits in the range of < 1 ppb for most compounds. For the analysis of low-molecular weight aldehydes, such as formaldehyde, acetaldehyde, propanal, and hexanal, lower detection limits were obtained when samples were converted to methoxime derivatives prior to injection. The detection limit for hexanal in water or Krebs-Ringer solution was 0.01 microM (10 pmol injected). The reproducibility of replicate injections was 4.4%. The usefulness of our system was illustrated by measuring aldehyde accumulation in peroxidized solutions of polyunsaturated fatty acids and rat tissue homogenates. Data confirmed that peroxidation of omega-3 fatty acids produces propanal, whereas omega-6 fatty acids form hexanal. Peroxidation of heart and brain homogenates formed predominantly propanal. However, the recovery of hexanal after sample treatment with methoxylamine depended on the derivatization time and temperature, suggesting that this aldehyde may form Schiff base linkages. These results show that spray extraction coupled to mass spectrometry provides a quick (< 1 min), clean and reproducible way to detect aldehydes produced from lipid peroxidation in aqueous samples.