Impact of N-acetylcysteine on endothelial function, B-type natriuretic peptide and renal function in patients with the cardiorenal syndrome: a pilot cross over randomised controlled trial

Role of mitochondria in reno-cardiac diseases: A study of bioenergetics, biogenesis, and GSH signaling in disease transition

Acute kidney injury (AKI) and chronic kidney disease (CKD) are global health burdens with rising prevalence. Their bidirectional relationship with cardiovascular dysfunction, manifesting as cardio-renal syndromes (CRS) types 3 and 4, underscores the interconnectedness and interdependence of these vital organ systems. Both the kidney and the heart are critically reliant on mitochondrial function. This organelle is currently recognized as a hub in signaling pathways, with emphasis on the redox regulation mediated by glutathione (GSH). Mitochondrial dysfunction, including impaired bioenergetics, redox, and biogenesis pathways, are central to the progression of AKI to CKD and the development of CRS type 3 and 4. This review delves into the metabolic reprogramming and mitochondrial redox signaling and biogenesis alterations in AKI, CKD, and CRS. We examine the pathophysiological mechanisms involving GSH redox signaling and the AMP-activated protein kinase (AMPK)-sirtuin (SIRT)1/3-peroxisome proliferator-activated receptor-gamma coactivator (PGC-1α) axis in these conditions. Additionally, we explore the therapeutic potential of GSH synthesis inducers in mitigating these mitochondrial dysfunctions, as well as their effects on inflammation and the progression of CKD and CRS types 3 and 4.

Systemic oxidative stress associates with disease severity and outcome in patients with new-onset or worsening heart failure

BACKGROUND

Oxidative stress may be a key pathophysiological mediator in the development and progression of heart failure (HF). The role of serum-free thiol concentrations, as a marker of systemic oxidative stress, in HF remains largely unknown.

OBJECTIVE

The purpose of this study was to investigate associations between serum-free thiol concentrations and disease severity and clinical outcome in patients with new-onset or worsening HF.

METHODS

Serum-free thiol concentrations were determined by colorimetric detection in 3802 patients from the BIOlogy Study to TAilored Treatment in Chronic Heart Failure (BIOSTAT-CHF). Associations between free thiol concentrations and clinical characteristics and outcomes, including all-cause mortality, cardiovascular mortality, and a composite of HF hospitalization and all-cause mortality during a 2-years follow-up, were reported.

RESULTS

Lower serum-free thiol concentrations were associated with more advanced HF, as indicated by worse NYHA class, higher plasma NT-proBNP (P < 0.001 for both) and with higher rates of all-cause mortality (hazard ratio (HR) per standard deviation (SD) decrease in free thiols: 1.253, 95% confidence interval (CI): 1.171-1.341, P < 0.001), cardiovascular mortality (HR per SD: 1.182, 95% CI: 1.086-1.288, P < 0.001), and the composite outcome (HR per SD: 1.058, 95% CI: 1.001-1.118, P = 0.046).

CONCLUSIONS

In patients with new-onset or worsening HF, a lower serum-free thiol concentration, indicative of higher oxidative stress, is associated with increased HF severity and poorer prognosis. Our results do not prove causality, but our findings may be used as rationale for future (mechanistic) studies on serum-free thiol modulation in heart failure. Associations of serum-free thiol concentrations with heart failure severity and outcomes.

A Systematic Review on the Protective Effect of N-Acetyl Cysteine Against Diabetes-Associated Cardiovascular Complications

INTRODUCTION

Heart failure is the leading cause of death in patients with diabetes. No treatment currently exists to specifically protect these patients at risk of developing cardiovascular complications. Accelerated oxidative stress-induced tissue damage due to persistent hyperglycemia is one of the major factors implicated in deteriorated cardiac function within a diabetic state. N-acetyl cysteine (NAC), through its enhanced capacity to endogenously synthesize glutathione, a potent antioxidant, has displayed abundant health-promoting properties and has a favorable safety profile.

OBJECTIVE

An increasing number of experimental studies have reported on the strong ameliorative properties of NAC. We systematically reviewed the data on the cardioprotective potential of this compound to provide an informative summary.

METHODS

Two independent reviewers systematically searched major databases, including PubMed, Cochrane Library, Google scholar, and Embase for available studies reporting on the ameliorative effects of NAC as a monotherapy or in combination with other therapies against diabetes-associated cardiovascular complications. We used the ARRIVE and JBI appraisal guidelines to assess the quality of individual studies included in the review. A meta-analysis could not be performed because the included studies were heterogeneous and data from randomized clinical trials were unavailable.

RESULTS

Most studies support the ameliorative potential of NAC against a number of diabetes-associated complications, including oxidative stress. We discuss future prospects, such as identification of additional molecular mechanisms implicated in diabetes-induced cardiac damage, and highlight limitations, such as insufficient studies reporting on the comparative effect of NAC with common glucose-lowering therapies. Information on the comparative analysis of NAC, in terms of dose selection, administration mode, and its effect on different cardiovascular-related markers is important for translation into clinical studies.

CONCLUSIONS

NAC exhibits strong potential for the protection of the diabetic heart at risk of myocardial infarction through inhibition of oxidative stress. The effect of NAC in preventing both ischemia and non-ischemic-associated cardiac damage is also of interest. Consistency in dose selection in most studies reported remains important in dose translation for clinical relevance.

The Role of Dendritic and Endothelial Cells in Cardiorenal Syndrome

BACKGROUNDS

Dendritic cells (DCs) are antigen-presenting cells that play a central role in innate and adaptive immune responses; however, the cross talk between cardiac and renal DCs in cardiorenal syndrome (CRS) has not yet been fully elucidated. In this setting, endothelial cells (ECs) also contribute to immune responses.

SUMMARY

DC and EC activation and dysfunction have a central role in the pathogenesis of CRS. Regarding immune responses in CRS, it is unknown whether ECs may serve as antigen-presenting cells or act synergistically with DCs to actively participate in innate and adaptive immune responses. This review first focuses on the burden of concomitant heart and renal DCs in the context of CRS; it examines what is known of DCs in animal models, and proposes a central role for DCs in all types of CRS. Second, this review briefly describes the role of ECs in the context of CRS. Key Messages: Understanding the role of DCs and ECs in immune response could lead to the development of novel therapies for the prevention and treatment of CRS.

Oral N-acetylcysteine and exercise tolerance in mild chronic obstructive pulmonary disease

Heightened oxidative stress is implicated in the progressive impairment of skeletal muscle vascular and mitochondrial function in chronic obstructive pulmonary disease (COPD). Whether accumulation of reactive oxygen species contributes to exercise intolerance in the early stages of COPD is unknown. The purpose of the present study was to determine the effects of oral antioxidant treatment with N-acetylcysteine (NAC) on respiratory, cardiovascular, and locomotor muscle function and exercise tolerance in patients with mild COPD. Thirteen patients [forced expiratory volume in 1 s (FEV₁)-to-forced vital capacity ratio < lower limit of normal (LLN) and FEV₁ ≥ LLN) were enrolled in a double-blind, randomized crossover study to receive NAC (1,800 mg/day) or placebo for 4 days. Severe-intensity constant-load exercise tests were performed with noninvasive measurements of central hemodynamics (stroke volume, heart rate, and cardiac output via impedance cardiography), arterial blood pressure, pulmonary ventilation and gas exchange, quadriceps muscle oxygenation (near-infrared spectroscopy), and estimated capillary blood flow. Nine patients completed the study with no major adverse clinical effects. Although NAC elevated plasma glutathione by ~27% compared with placebo (P < 0.05), there were no differences in exercise tolerance (placebo: 325 ± 47 s, NAC: 336 ± 51 s), central hemodynamics, arterial blood pressure, pulmonary ventilation or gas exchange, locomotor muscle oxygenation, or capillary blood flow from rest to exercise between conditions (P > 0.05 for all). In conclusion, modulation of plasma redox status with oral NAC treatment was not translated into beneficial effects on central or peripheral components of the oxygen transport pathway, thereby failing to improve exercise tolerance in nonhypoxemic patients with mild COPD.NEW & NOTEWORTHY Acute antioxidant treatment with N-acetylcysteine (NAC) elevated plasma glutathione but did not modulate central or peripheral components of the O₂ transport pathway, thereby failing to improve exercise tolerance in patients with mild chronic obstructive pulmonary disease (COPD).

The Central Role of Endothelial Dysfunction in Cardiorenal Syndrome

BACKGROUND

Endothelial dysfunction (ED) has emerged as a critical process in cardiorenal syndrome (CRS). The concept that ED is closely linked with cardiac and renal dysfunction has become an important target for CRS-related research and clinical practice.

SUMMARY

The sequence of events leading to ED is initiated by type I endothelial activation (almost immediately) and type II endothelial activation (over hours, days, and even months), followed by endothelial apoptosis and endothelial necrosis. The fact that ED is a continual cellular event divides this process into reversible ED (endothelial activation) and irreversible ED (endothelial apoptosis and necrosis). This basic research-defined concept may have clinical implications. Although most antihypertensive drugs (ACE inhibitors, statins, etc.) are effective in patients with hypertension and diabetes, some of them have proved to be ineffective, which may partly be attributed to irreversible ED. Even though the etiology of ED consists mainly of asymmetric dimethylarginine, nitric oxide, oxidative stress, and anti-endothelial cell antibodies, many other inducers of ED have been identified. In addition, a distinct role of ED has been reported for each type of CRS in humans.

KEY MESSAGES

Further study is warranted to prove whether ED holds promise as a pharmacological target in CRS patients.

Mitochondrial reactive oxygen species at the heart of the matter: new therapeutic approaches for cardiovascular diseases

Reactive oxygen species (ROS) have been implicated in a variety of age-related diseases, including multiple cardiovascular disorders. However, translation of ROS scavengers (antioxidants) into the clinic has not been successful. These antioxidants grossly reduce total levels of cellular ROS including ROS that participate in physiological signaling. In this review, we challenge the traditional antioxidant therapeutic approach that targets ROS directly with novel approaches that improve mitochondrial functions to more effectively treat cardiovascular diseases.

Effects of oral N-acetylcysteine on walking capacity, leg reactive hyperemia, and inflammatory and angiogenic mediators in patients with intermittent claudication

Increased oxidative stress and inflammation contribute to impaired walking capacity and endothelial dysfunction in patients with intermittent claudication (IC). The goal of the study was to determine the effects of oral treatment with the antioxidant N-acetylcysteine (NAC) on walking capacity, leg postocclusive reactive hyperemia, circulating levels of inflammatory mediators, and whole blood expression of angiogenic mediators in patients with IC. Following a double-blinded randomized crossover design, 10 patients with IC received NAC (1,800 mg/day for 4 days plus 2,700 mg before the experimental session) and placebo (PLA) before undergoing a graded treadmill exercise test. Leg postocclusive reactive hyperemia was assessed before and after the test. Blood samples were taken before and after NAC or PLA ingestions and 5 and 30 min after the exercise test for the analysis of circulating inflammatory and angiogenic markers. Although NAC increased the plasma ratio of reduced to oxidized glutathione, there were no differences between experimental sessions for walking tolerance and postocclusive reactive hyperemia. Plasma concentrations of soluble vascular cell adhesion protein-1, monocyte chemotactic protein-1, and endothelin-1 increased similarly following maximal exercise after PLA and NAC (P < 0.001). Whole blood expression of pro-angiogenic microRNA-126 increased after maximal exercise in the PLA session, but treatment with NAC prevented this response. Similarly, exercise-induced changes in whole blood expression of VEGF, endothelial nitric oxide synthase and phosphatidylinositol 3-kinase R2 were blunted after NAC. In conclusion, oral NAC does not increase walking tolerance or leg blood flow in patients with IC. In addition, oral NAC prevents maximal exercise-induced increase in the expression of circulating microRNA-126 and other angiogenic mediators in patients with IC.

Apocynin Attenuates Cardiac Injury in Type 4 Cardiorenal Syndrome via Suppressing Cardiac Fibroblast Growth Factor-2 With Oxidative Stress Inhibition

Background

Type 4 cardiorenal syndrome (CRS) refers to the cardiac injury induced by chronic kidney disease. We aimed to assess oxidative stress and cardiac injury in patients with type 4 CRS, determine whether the antioxidant apocynin attenuated cardiac injury in rats with type 4 CRS, and explore potential mechanisms.

Methods and Results

A cross-sectional study was conducted among patients with type 4 CRS (n=17) and controls (n=16). Compared with controls, patients with type 4 CRS showed elevated oxidative stress, which was significantly correlated with cardiac hypertrophy and decreased ejection fraction. In vivo study, male Sprague-Dawley rats underwent 5/6 subtotal nephrectomy and sham surgery, followed with apocynin or vehicle treatment for 8 weeks. Eight weeks after surgery, the 5/6 subtotal nephrectomy rats mimicked type 4 CRS, showing increased serum creatinine, cardiac hypertrophy and fibrosis, and decreased ejection fraction compared with sham-operated animals. Cardiac malondialdehyde, NADPH oxidase activity, fibroblast growth factor-2, and extracellular signal-regulated kinase 1/2 (ERK1/2) phosphorylation increased significantly in the 5/6 subtotal nephrectomy rats. These changes were significantly attenuated by apocynin. In vitro study showed that apocynin reduced angiotensin II–induced NADPH oxidase–dependent oxidative stress, upregulation of fibroblast growth factor-2 and fibrosis biomarkers, and ERK1/2 phosphorylation in cardiac fibroblasts. Importantly, the ERK1/2 inhibitor U0126 reduced the upregulation of fibroblast growth factor-2 and fibrosis biomarkers in angiotensin II–treated fibroblasts.

Conclusions

Oxidative stress is a candidate mediator for type 4 CRS. Apocynin attenuated cardiac injury in type 4 CRS rats via inhibiting NADPH oxidase–dependent oxidative stress-activated ERK1/2 pathway and subsequent fibroblast growth factor-2 upregulation. Our study added evidence to the beneficial effect of apocynin in type 4 CRS.

Improved oxidative status in major abdominal surgery patients after N-acetyl cystein supplementation

Background

Increased levels of reactive oxygen species during and after surgery may affect inflammatory response, post-operative adhesion molecule formation, and hemodynamic stability. The glutathione redox cycle is an important regulator in oxidative stress and its reduced forms scavenge free radicals. N-acetyl cysteine, a precursor of reduced glutathione, is considered as a potentially therapeutic wide spectrum agent in clinical practice. We therefore examined whether N-acetyl cysteine improves some biochemical parameters in cancer patients undergoing major abdominal surgery.

Methods

Thirty-three patients diagnosed with pancreas, stomach, rectum, colon malignancies, and undergoing major abdominal surgery at Ankara Numune Training and Research Hospital were randomly divided into two groups; control (CON) and N-acetyl cysteine (NAC). The NAC group had 1,200 mg N-acetyl cysteine starting two days before the operation day, in addition to isonitrogenous and isocaloric total parenteral nutrition of 1.2 g/kg protein, 25 kcal/kg, and 60:40 carbohydrate/fat ratio. Blood and urine samples were drawn two days before the operation, on operation day, and on the first, third, and fifth days post-operation.

Results

Plasma malondialdehyde was significantly lower in the NAC group (P < 0.001). N-acetyl cysteine treatment did not affect plasma levels of vitamin A, C or E. The NAC group exhibited a higher ratio of reduced glutathione to oxidised glutathione (P = 0.019). Urinary nitrate level was also significantly lower in the NAC group (P = 0.016).

Conclusion

The study demonstrated the clinical importance of N-acetyl cysteine supplementation on antioxidant parameters in abdominal surgery patients. In these patients N-acetyl cysteine and vitamin administration can be considered as an effective method for improvement of oxidative status.