Effect of N-acetylcysteine treatment on the expression of leukocyte surface markers after burn injury

Effects of Sulfur Amino Acids on Cardiodynamic Parameters of Isolated Rat Heart

Sulfur-containing amino acids are integral part of molecular mechanisms which underlie many aspects of cellular function and homeostasis, facilitated by reversible changes in oxidation states of sulfur atoms. Dysregulation of these pathways is associated with diverse pathologies, notably of the cardiovascular system, which are typically characterized by inappropriate plasma levels of sulfur-containing amino acids. The aim of this study was to assess the acute, direct effects of sulfur-containing amino acids and inorganic NaHS, as H2S donor, on cardiodynamic parameters in homocysteine treated rats. Moderate hyperhomocysteinemia did not cause significant decrease in myocardial contractility, but our findings suggest that NaHS and L-methionine cause negative effects on cardiac function in hearts of the rats treated with homo-cysteine, even in a single administration. Further investigations need to be carried out with purpose of better understanding and highlightening the impact of Hcy and sulphur amino acids on cardiac function.

The effects of L-cysteine and N-acetyl-L-cysteine on homocysteine metabolism and haemostatic markers, and on cardiac and aortic histology in subchronically methionine-treated Wistar male rats

Methionine is the precursor of homocysteine, a sulfur amino acid intermediate in the methylation and transsulfuration pathways; methionine-rich diets were used to induce hyperhomocysteinemia, and cardiovascular pathology was often observed. Other sulfur amino acids interfere with this metabolism, i.e., L-cysteine (Cys) and N-aceyl-L-cysteine (NAC), and probably also affect cardiovascular system. Their effects are controversial due to their ability to act both as anti- or pro-oxidant. Thus, this study aimed to elucidate their influence on levels of homocysteine, folate and vitamin B12, levels of different haemostatic parameters (fibrinogen, D-dimer, vWF Ag, vWF Ac) in rat serum or plasma as well as their effects on cardiac and aortic tissue histology in subchronically methionine-treated rats. Wistar albino rats were divided into 4 experimental groups: (a) control group (0.9% sodium chloride 0.1-0.2 mL/day) (n = 10) (K); (b) DL-methionine (0.8 mmol/kg/bw/day) (n = 10) (M); (c) DL-methionine (0.8 mmol/kg/bw/day) + L-cysteine (7 mg/kg/bw/day) (n = 8) (C); (d) DL-methionine (0.8 mmol/ kg/bw/day) + N-acetyl-L-cysteine (50 mg/kg/bw/day) (n = 8) (N). All substances were applied i.p., treatment duration 3 weeks. Lower levels of vitamin B12 in all the groups were found. Folate was reduced only in N group. Decreased fibrinogen was noted in C and N groups and increased D-dimer only in C. VWF activity was reduced in M and C groups. Deleterious effects in heart were observed, especially after Cys and NAC application. Aortic tissue remained unchanged. In conclusion, it could be said that sulfur amino acids have the significant impact on cardiovascular system in subchronically methionine-treated rats. This study points out the relevance of their complex interactions and deleterious effects mediated by either direct influence or procoagulant properties.

Evidence of a Redox-Dependent Regulation of Immune Responses to Exercise-Induced Inflammation

We used thiol-based antioxidant supplementation (n-acetylcysteine, NAC) to determine whether immune mobilisation following skeletal muscle microtrauma induced by exercise is redox-sensitive in healthy humans. According to a two-trial, double-blind, crossover, repeated measures design, 10 young men received either placebo or NAC (20 mg/kg/day) immediately after a muscle-damaging exercise protocol (300 eccentric contractions) and for eight consecutive days. Blood sampling and performance assessments were performed before exercise, after exercise, and daily throughout recovery. NAC reduced the decline of reduced glutathione in erythrocytes and the increase of plasma protein carbonyls, serum TAC and erythrocyte oxidized glutathione, and TBARS and catalase activity during recovery thereby altering postexercise redox status. The rise of muscle damage and inflammatory markers (muscle strength, creatine kinase activity, CRP, proinflammatory cytokines, and adhesion molecules) was less pronounced in NAC during the first phase of recovery. The rise of leukocyte and neutrophil count was decreased by NAC after exercise. Results on immune cell subpopulations obtained by flow cytometry indicated that NAC ingestion reduced the exercise-induced rise of total macrophages, HLA⁺ macrophages, and 11B⁺ macrophages and abolished the exercise-induced upregulation of B lymphocytes. Natural killer cells declined only in PLA immediately after exercise. These results indicate that thiol-based antioxidant supplementation blunts immune cell mobilisation in response to exercise-induced inflammation suggesting that leukocyte mobilization may be under redox-dependent regulation.

Role of the immune system in hypertension: modulation by dietary antioxidants

Hypertension is a major health problem worldwide. Individuals with hypertension are at an increased risk for stroke, heart disease, and kidney failure. Although the etiology of essential hypertension has a genetic component, lifestyle factors such as diet play an important role. Insulin resistance is a common feature of hypertension in both humans and animal models affecting glucose and lipid metabolism producing excess aldehydes including methylglyoxal. These aldehydes react with proteins to form conjugates called advanced glycation end products (AGEs). This alters protein structure and function and can affect vascular and immune cells leading to their activation and secretion of inflammatory cytokines. AGEs also act via receptors for advanced glycation end products on these cells altering the function of antioxidant and metabolic enzymes, and ion channels. This results in an increase in cytosolic free calcium, decrease in nitric oxide, endothelial dysfunction, oxidative stress, peripheral vascular resistance, and infiltration of vascular and kidney tissue with inflammatory cells leading to hypertension. Supplementation with dietary antioxidants including vitamins C, E, or B(6), thiols such as cysteine and lipoic acid, have been shown to lower blood pressure and plasma inflammatory cytokines in animal models and humans with essential hypertension. A well-balanced diet rich in antioxidants that includes vegetables, fruits, low fat dairy products, low salt, and includes whole grains, poultry, fish and nuts, lowers blood pressure and vascular inflammation. These antioxidants may achieve their antihypertensive and anti-inflammatory/immunomodulatory effects by reducing AGEs and improving insulin resistance and associated alterations. Dietary supplementation with antioxidants may be a beneficial, inexpensive, front-line alterative treatment modality for hypertension.

N-acetylcysteine expresses powerful anti-inflammatory and antioxidant activities resulting in complete improvement of acetic acid-induced colitis in rats

High free radical production, low antioxidant capacity and excessive inflammation are well known features in the pathogenesis of inflammatory bowel disease. N-acetylcysteine (NAC) is a powerful antioxidant and a scavenger of hydroxyl radicals. Recently, NAC has also been shown to have anti-inflammatory activities in tissues. Our study objective was to investigate the effects of NAC on tissue inflammatory activities using an ulcerative colitis model induced by acetic acid (AA) in rats. Wistar rats (n = 32) were divided into four groups. AA-induced colitis was performed in two of the groups while the other two groups were injected with saline intrarectally. One of the AA-induced colitis groups and one of the control groups were administered NAC (500 mg/kg/day) intrarectally, and the other control groups were given saline. After 4 days, colonic changes were evaluated biochemically by measuring proinflammatory cytokines [tumor necrosis factor (TNF)-α, interleukin (IL)-1β and IL-6], myeloperoxidase (MPO), malondialdehyde (MDA), glutathione (GSH) and superoxide dismutase (SOD) levels in tissue homogenates and by histopathological examination. AA caused colonic mucosal injury, whereas NAC administration suppressed these changes in the AA-induced colitis group (p < 0.001). AA-administration resulted in increased TNF-α, IL-1β, IL-6, MPO and MDA levels, and decreased GSH and SOD levels, whereas NAC reversed these effects (all p < 0.001). In conclusion, the present study proposes that intrarectal NAC therapy has a dual action as an effective anti-inflammatory and an antioxidant, and may be a promising therapeutic option for ulcerative colitis.

N-acetylcysteine for sepsis and systemic inflammatory response in adults

BACKGROUND

Death is common in systemic inflammatory response syndrome (SIRS) or sepsis-induced multisystem organ failure and it has been thought that antioxidants such as N-acetylcysteine could be beneficial.

OBJECTIVES

We assessed the clinical effectiveness of intravenous N-acetylcysteine for the treatment of patients with SIRS or sepsis.

SEARCH METHODS

We searched the following databases: Cochrane Central Register of Clinical Trials (CENTRAL) (The Cochrane Library 2011, Issue 12); MEDLINE (January 1950 to January 2012); EMBASE (January 1980 to January 2012); CINAHL (1982 to January 2012); the NHS Trusts Clinical Trials Register and Current Controlled Trials (www.controlled-trials.com); LILACS; KoreaMED; MEDCARIB; INDMED; PANTELEIMON; Ingenta; ISI Web of Knowledge and the National Trials Register to identify all relevant randomized controlled trials available for review.

SELECTION CRITERIA

We included only randomized controlled trials (RCTs) in the meta-analysis.

DATA COLLECTION AND ANALYSIS

We independently performed study selection, quality assessment and data extraction. We estimated risk ratios (RR) for dichotomous outcomes. We measured statistical heterogeneity using the I(2) statistic.

MAIN RESULTS

We included 41 fully published studies (2768 patients). Mortality was similar in the N-acetylcysteine group and the placebo group (RR 1.06, 95% CI 0.79 to 1.42; I(2) = 0%). Neither did N-acetylcysteine show any significant effect on length of stay, duration of mechanical ventilation or incidence of new organ failure. Early application of N-acetylcysteine to prevent the development of an oxidato-inflammatory response did not affect the outcome, nor did late application that is after 24 hours of developing symptoms. Late application was associated with cardiovascular instability.

AUTHORS' CONCLUSIONS

Overall, this meta-analysis puts doubt on the safety and utility of intravenous N-acetylcysteine as an adjuvant therapy in SIRS and sepsis. At best, N-acetylcysteine is ineffective in reducing mortality and complications in this patient population. At worst, it can be harmful, especially when administered later than 24 hours after the onset of symptoms, by causing cardiovascular depression. Unless future RCTs provide evidence of treatment effect, clinicians should not routinely use intravenous N-acetylcysteine in SIRS or sepsis and academics should not promote its use.