N-acetylcysteine inhibits in vivo nitric oxide production by inducible nitric oxide synthase

NRF2 is a spatiotemporal metabolic hub essential for the polyfunctionality of Th2 cells

Upon encountering allergens, CD4+ T cells differentiate into IL-4-producing Th2 cells in lymph nodes, which later transform into polyfunctional Th2 cells producing IL-5 and IL-13 in inflamed tissues. However, the precise mechanism underlying their polyfunctionality remains elusive. In this study, we elucidate the pivotal role of NRF2 in polyfunctional Th2 cells in murine models of allergic asthma and in human Th2 cells. We found that an increase in reactive oxygen species (ROS) in immune cells infiltrating the lungs is necessary for the development of eosinophilic asthma and polyfunctional Th2 cells in vivo. Deletion of the ROS sensor NRF2 specifically in T cells, but not in dendritic cells, significantly abolished eosinophilia and polyfunctional Th2 cells in the airway. Mechanistically, NRF2 intrinsic to T cells is essential for inducing optimal oxidative phosphorylation and glycolysis capacity, thereby driving Th2 cell polyfunctionality independently of IL-33, partially by inducing PPARγ. Treatment with an NRF2 inhibitor leads to a substantial decrease in polyfunctional Th2 cells and subsequent eosinophilia in mice and a reduction in the production of Th2 cytokines from peripheral blood mononuclear cells in asthmatic patients. These findings highlight the critical role of Nrf2 as a spatial and temporal metabolic hub that is essential for polyfunctional Th2 cells, suggesting potential therapeutic implications for allergic diseases.

Targeting the Multiple Complex Processes of Hypoxia-Ischemia to Achieve Neuroprotection

Hypoxic-ischemic encephalopathy (HIE) is a major cause of newborn brain damage stemming from a lack of oxygenated blood flow in the neonatal period. Twenty-five to fifty percent of asphyxiated infants who develop HIE die in the neonatal period, and about sixty percent of survivors develop long-term neurological disabilities. From the first minutes to months after the injury, a cascade of events occurs, leading to blood-brain barrier (BBB) opening, neuronal death and inflammation. To date, the only approach proposed in some cases is therapeutic hypothermia (TH). Unfortunately, TH is only partially protective and is not applicable to all neonates. This review synthesizes current knowledge on the basic molecular mechanisms of brain damage in hypoxia-ischemia (HI) and on the different therapeutic strategies in HI that have been used and explores a major limitation of unsuccessful therapeutic approaches.

Restoration of injured motoneurons reduces microglial proliferation in the adult rat facial nucleus

In the axotomized facial nucleus (axotFN), the levels of choline acetyltransferase, vesicular acetylcholine transporter, and gamma amino butyric acid A receptor α1 are decreased, after which the microglia begin to proliferate around injured motoneuron cell bodies. We conjectured that an injury signal released from the injured motoneurons triggers the microglial proliferation in the axotFN. However, it is unclear whether the level of microglial proliferation is dependent on the degree of motoneuronal insult. In this study, we investigated the relationship between the extents of motoneuronal injury and microglial proliferation in a rat axotFN model. Administration of glial cell line-derived neurotrophic factor, N-acetyl L-cysteine, or salubrinal at the transection site ameliorated the increase in c-Jun and the reductions in levels of phosphorylated cAMP response element binding protein (p-CREB) and functional molecules in the injured motoneurons. Concurrently, the levels of the microglial marker ionized calcium-binding adapter molecule 1 and of macrophage colony-stimulating factor (cFms), proliferating cell nuclear antigen, and p-p38/p38 were significantly downregulated in microglia. These results demonstrate that the recovery of motoneuron function resulted in the reduction in microglial proliferation. We conclude that the degree of neuronal injury regulates the levels of microglial proliferation in the axotFN.

Effects of N-acetylcysteine on oxidative stress biomarkers, depression, and anxiety symptoms in patients with multiple sclerosis

AIM

N-acetylcysteine (NAC), a thiol-containing antioxidant and glutathione (GSH) precursor, attenuates oxidative stress, and possibly improves psychiatric disorders. This study aimed to evaluate the effects of oral NAC on oxidative stress, depression, and anxiety symptoms in patients with multiple sclerosis (MS).

METHODS

This clinical trial was conducted on 42 MS patients randomly assigned to intervention (n = 21) and control (n = 21) groups. The intervention group received 600 mg of NAC twice daily for 8 weeks, and the control group received a placebo with the same prescription form. An analysis of serum malondialdehyde (MDA), serum nitric oxide (NO), and erythrocyte GSH was carried out on both groups, along with a complete blood count. The Hospital Anxiety and Depression Scale (HADS) was used to assess symptoms of depression (HADS-D) and anxiety (HADS-A).

RESULTS

Compared to the control group, NAC consumption significantly decreased serum MDA concentrations (-0.33 [-5.85-2.50] vs. 2.75 [-0.25-5.22] μmol/L; p = 0.03) and HADS-A scores (-1.6 ± 2.67 vs. 0.33 ± 2.83; p = 0.02). No significant changes were observed in serum NO concentrations, erythrocyte GSH levels, and HADS-D scores (p > 0.05).

CONCLUSIONS

Based on the findings of the present study, NAC supplementation for 8 weeks decreased lipid peroxidation and improved anxiety symptoms in MS patients. The aforementioned results suggest that adjunctive therapy with NAC can be considered an effective strategy for MS management. Further randomized controlled studies are warranted.

N-Acetylcysteine Administration Attenuates Sensorimotor Impairments Following Neonatal Hypoxic-Ischemic Brain Injury in Rats

Hypoxic ischemic (HI) brain injury that occurs during neonatal period has been correlated with severe neuronal damage, behavioral deficits and infant mortality. Previous evidence indicates that N-acetylcysteine (NAC), a compound with antioxidant action, exerts a potential neuroprotective effect in various neurological disorders including injury induced by brain ischemia. The aim of the present study was to investigate the role of NAC as a potential therapeutic agent in a rat model of neonatal HI brain injury and explore its long-term behavioral effects. To this end, NAC (50 mg/kg/dose, i.p.) was administered prior to and instantly after HI, in order to evaluate hippocampal and cerebral cortex damage as well as long-term functional outcome. Immunohistochemistry was used to detect inducible nitric oxide synthase (iNOS) expression. The results revealed that NAC significantly alleviated sensorimotor deficits and this effect was maintained up to adulthood. These improvements in functional outcome were associated with a significant decrease in the severity of brain damage. Moreover, NAC decreased the short-term expression of iNOS, a finding implying that iNOS activity may be suppressed and that through this action NAC may exert its therapeutic action against neonatal HI brain injury.

Nitro Capsaicin Suppressed Microglial Activation and TNF-α-Induced Brain Microvascular Endothelial Cell Damage

Chronically activated microglia and brain vascular damage are major causes of neuroinflammation. The aim of this study was to determine the anti-inflammatory effects of nitro capsaicin, a newly modified capsaicin with less irritating characteristics, against microglial activation and brain microvascular endothelial cell damage. Using the SIMA9 microglia cell line, we found that nitro capsaicin reduced nitric oxide (NO) production in LPS-activated microglia better than its parent compound, capsaicin. Nitro capsaicin also decreased the expression of proinflammatory cytokines (TNF-α, IL-1β, and IL-6) and enhanced the levels of anti-inflammatory factors, IL-4 and IL-10, both at the mRNA and protein levels. In the TNF-α-induced vascular damage model, nitro capsaicin decreased expression and secretion of the proinflammatory cytokines IL-1β and IL-6. Phosphorylated NF-κB p65, a key transcription factor that stimulates the signaling of inflammatory pathways, was also reduced in the presence of nitro capsaicin, suggesting that the anti-inflammatory effects of nitro capsaicin were created through reducing NF-κB activation. Together, we concluded that nitro capsaicin has the potential to be further developed as an anti-neuroinflammatory agent.

An Activatable Probe with Aggregation-Induced Emission for Detecting and Imaging Herbal Medicine Induced Liver Injury with Optoacoustic Imaging and NIR-II Fluorescence Imaging

Whilte herbal medicines are widely used for health promotion and therapy for chronic conditions, inappropriate use of them may cause adverse effects like liver injury, and accurately evaluating their hepatotoxicity is of great significance for public health. Herein, an activatable probe QY-N for diagnosing herbal-medicine-induced liver injury by detecting hepatic NO with NIR-II fluorescence and multispectral optoacoustic tomography (MSOT) imaging is demonstrated. The probe includes a bismethoxyphenyl-amine-containing dihydroxanthene serving as electron donor, a quinolinium as electron acceptor, and a butylamine as recognition group and fluorescence quencher. The hepatic level of NO reacts with butylamine, thereby generating the activated probe QY-NO which exhibits a red-shifted absorption band (700-850 nm) for optoacoustic imaging and generates strong emission (910-1110 nm) for NIR-II fluorescence imaging. QY-NO is aggregation-induced-emission (AIE) active, which ensures strong emission in aggregated state. QY-N is utilized in the triptolide-induced liver injury mouse model, and experimental results demonstrate the QY-N can be activated by hepatic NO and thus be used in detecting herbal-medicine-induced liver injury. The temporal and spatial information provided by three-dimensional MSOT images well delineates the site and size of liver injury. Moreover, QY-N has also been employed to monitor rehabilitation of liver injury during treatment process.

Analysis of N-acetyl cysteine modified polydimethylsiloxane shunt for improved treatment of hydrocephalus

A major cause of hydrocephalus shunt failure is cell adhesion and obstruction of shunt catheter holes. An estimated 50% of pediatric shunts fail in the first 2 years of insertion, decreasing cell attachment and catheter obstruction can prolong the lifetime and effectiveness of the device. From previous studies, it was shown that treatment of the polydimethylsiloxane (PDMS) surface of a standard catheter with an N-acetyl-cysteine (NAC/1-ethyl-3-(3-dimethylanimopropyl)carbodiimide hydrochloride/N-hydroxysuccinimide) layer increases the wettability of the surface and has been shown to decrease cell adhesion. Other studies indicate that NAC's antioxidant behavior induces glutathione and in turn modulates cell inflammatory pathways. The current study explores the longevity of the NAC coating from the surface of the catheter over time and shows its effect on valve function. Using SEM imaging, contact angle testing, and nanodrop spectrophotometry, this release was quantified for shunt samples incubated for 0, 10, 30, 60, and 90 days. Contact angle showed a significant increase in wettability of the surface when shunts were treated with NAC, confirming successful surface modification. Pressure assays determined that if the coating is release it had no detrimental downstream effects, such as on the shunt valve mechanism. SEM imaging revealed slight deformations in surface coating indicative of salt deposition on the modified shunt samples, while nanodrop spectrophotometry and contact angle data trends suggested some discharge of the NAC coating from the catheter surfaces. The effects of NAC on cell activity may transform the way hydrocephalus is treated in the future by increasing the longevity of the shunt to protect from obstruction.

HEMA-induced oxidative stress inhibits NF-κB nuclear translocation and TNF release from LTA- and LPS-stimulated immunocompetent cells

OBJECTIVE

The release of inflammatory cytokines from antigen-stimulated cells of the immune system is inhibited by resin monomers such as 2-hydroxyethyl methacrylate (HEMA). Although the formation of oxidative stress in cells exposed to HEMA is firmly established, the mechanism behind the inhibited cytokine secretion is only partly known. The present investigation presents evidence regarding the role of HEMA-induced oxidative stress in the secretion of the pro-inflammatory cytokine TNFα from cells exposed to the antigens LTA (lipoteichoic acid) or LPS (lipopolysaccharide) of cariogenic microorganisms using BSO (L-buthionine sulfoximine) or NAC (N-acetyl cysteine) to inhibit or stabilize the amounts of the antioxidant glutathione.

METHOD

RAW264.7 mouse macrophages were treated with LTA, LPS or HEMA in the presence of BSO or NAC for 1h or 24h. Secretion of TNFα from cell cultures was analyzed by ELISA, and the formation of reactive oxygen (ROS) or nitrogen species (RNS) was determined by flow cytometry. Protein expression was detected by Western blotting.

RESULTS

The release of TNFα in both LTA- and LPS-exposed cells was decreased by HEMA, and this concentration-dependent inhibitory effect was amplified by BSO or NAC. LTA- and LPS-stimulated expression of the redox-sensitive transcription factor NF-αB (p65) in cell nuclei decreased in the presence of HEMA because the translocation of p65 from the cytosol was prevented by oxidative stress specifically increased by the monomer.

CONCLUSIONS

A disturbance of the cellular redox balance, particularly induced by HEMA, is a crucial factor in the inhibition of LTA- and LPS-stimulated signalling pathways leading to TNFα secretion.

The Effects of Treatment with N-Acetyl Cysteine on Clinical Signs in Persistent Breeding-Induced Endometritis Susceptible Mares

Persistent breeding-induced endometritis (PBIE) is a major cause of infertility in mares. Endometrial inflammation that persists until embryonic descent ultimately results in early embryonic death. A poor endometrial biopsy grade (IIb or III) has been identified as a risk factor for PBIE. Intrauterine fluid accumulation (>2 cm in depth), pathologic endometrial edema, and elevated intrauterine neutrophil levels are all clinical features of PBIE. Commonly applied treatment options include uterine lavage and oxytocin therapy. N-acetyl cysteine (NAC), a mucolytic used to treat bacterial endometritis in mares, has anti-inflammatory properties and was investigated as a potential treatment for PBIE. A randomized, blinded, cross-over design clinical trial used NAC before breeding in PBIE-susceptible mares (n = 9). Intrauterine infusion of 3.3% NAC was performed 12 hours before insemination, and endometrial cytology and endometrial biopsy samples were obtained at 12 and 60 hours after insemination. Endometrial biopsies were evaluated for the degree of inflammation present. Clinical signs of endometrial edema and intrauterine fluid volumes were assessed by transrectal ultrasound at 12 and then every 24 hours after breeding. Data were analyzed using repeated measures analysis of variance and a Mann Whitney Wilcoxon Test. Treatment with NAC did not improve clinical signs in PBIE-affected mares. However, endometrial biopsies from mares treated with NAC displayed more diffuse and severe neutrophil infiltration than control cycles. Further research using a larger population of mares is required to evaluate the effects of NAC treatment on the endometrium of PBIE-susceptible mares.

Degrading products of chondroitin sulfate can induce hypertrophy-like changes and MMP-13/ADAMTS5 production in chondrocytes

Chondroitin sulfate (CS) is the most abundant glycosaminoglycan (GAG) in articular cartilage and the loss of CS-GAG occurs early in OA. As a major component of perichondral matrix interacting directly with chondrocytes, the active turnover of CS can affect to break the homeostasis of chondrocytes. Here we employ CS-based 3-dimensional (3D) hydrogel scaffold system to investigate how the degradation products of CS affect the catabolic phenotype of chondrocytes. The breakdown of CS-based ECM by the chondroitinase ABC (ChABC) resulted in a hypertrophy-like morphologic change in chondrocytes, which was accompanied by catabolic phenotypes, including increased MMP-13 and ADAMTS5 expression, nitric oxide (NO) production and oxidative stress. The inhibition of Toll-like receptor 2 (TLR2) or TLR4 with OxPAPC (TLR2 and TLR4 dual inhibitor) and LPS-RS (TLR4-MD2 inhibitor) ameliorated these catabolic phenotypes of chondrocytes by CS-ECM degradation, suggesting a role of CS breakdown products as damage-associated molecular patterns (DAMPs). As downstream signals of TLRs, MAP kinases, NF-kB, NO and STAT3-related signals were responsible for the catabolic phenotypes of chondrocytes associated with ECM degradation. NO in turn reinforced the activation of MAP kinases as well as NFkB signaling pathway. Thus, these results propose that the breakdown product of CS-GAG can recapitulate the catabolic phenotypes of OA.

Antinociceptive and anti-inflammatory effects of N-acetylcysteine and verapamil in Wistar rats

Background

Antinociceptive anti-inflammatory drugs have many adverse effects. The goal of this investigation is to study the probable anti-inflammatory and analgesic effects of verapamil and N-acetylcysteine (NAC) in experimental rats.

Methods

Adult male Wistar rats were randomly divided into 4 groups in the antinociceptive study, each containing 6 rats; the normal control group, which received saline (1 mL/kg); the diclofenac group, which received diclofenac sodium (5 mg/kg); the NAC group, which received NAC (125 mg/kg); and the verapamil group, which received verapamil (8 mg/kg). In the anti-inflammatory study, 5 groups were used, the 4 previous groups with the addition of an edema control group, received saline and were subjected to formalin test. Hot plate latency time was recorded for antinociceptive evaluation. Paw edema thickness and biochemical parameters were recorded for anti-inflammatory evaluation.

Results

Administration of NAC showed significant prolongation of hot plate latency time at 1 hour when compared to the control group while verapamil showed a significant prolongation of hot plate latency time at 1 and 2 hours when compared to the control group and NAC group values. Administration of NAC and verapamil significantly decreased paw edema thickness at 2, 4, and 8 hours when compared to edema control values. Regarding biochemical markers, NAC and verapamil significantly decreased serum nitric oxide synthase, C-reactive protein, and cyclooxygenase- 2 levels compared to the edema control value. In accordance, a marked improvement of histopathological findings was observed with both drugs.

Conclusions

NAC and verapamil have antinociceptive and anti-inflammatory effects comparable to diclofenac sodium.

Beneficial Effects of N-Acetyl-L-cysteine or Taurine Pre- or Post-treatments in the Heart, Spleen, Lung, and Testis of Hexavalent Chromium-Exposed Mice

Hexavalent chromium[Cr(VI)] compounds may induce toxic effects, possibly via reactive intermediates and radicals formed during Cr(VI) reduction. In this study, we probed the possible effects of N-acetyl-L-cysteine (NAC) and taurine pre- or post-treatments on Cr(VI)-induced changes in lipid peroxidation and nonprotein thiols (NPSH) in mice heart, lung, spleen, and testis tissues. The mice were randomly assigned to six groups, consisting of control, Cr(VI)-exposed (20 mg Cr/kg, intraperitoneal ,ip), NAC (200 mg/kg, ip) as pre-treatment and post-treatment, and taurine (1 g/kg, ip) pre-treatment and post-treatment groups. Lipid peroxidation and NPSH levels were determined and the results were compared with regard to tissue- and antioxidant-specific basis. Exposure to Cr(VI) significantly increased lipid peroxidation in all tissues as compared to the control (p < 0.05); and consistent with this data, NPSH levels were significantly decreased (p < 0.05). Notably, administration of NAC and taurine, either before or after Cr(VI) exposure, was able to ameliorate the lipid peroxidation (p < 0.05) in all tissues. In the case of NPSH content, while the decline could be alleviated by both NAC and taurine pre- and post-treatments in the spleen, diverging results were obtained in other tissues. The effects of Cr(VI) on the lung thiols were abolished by pre-treatment with NAC and taurine; however, post-treatments could not exert significant effect. While thiol depletion in the heart was totally replenished by NAC and taurine administrations, NAC pre-treatment was partially more effective than post-treatment. In contrast with lipid peroxidation data, NAC treatment could not provide a statistically significant beneficial effect on NPSH content of the testis, whereas the effect in this tissue by taurine was profound. Thus, these data highlight the importance of tissue-specific factors and the critical role of administration time. Overall, our data suggest that NAC and taurine may have potential in prevention of Cr(VI)-induced toxicity in the heart, lung, spleen, and testis tissues.

Nitric oxide triggers the assembly of "type II" stress granules linked to decreased cell viability

We show that 3-morpholinosydnonimine (SIN-1)-induced nitric oxide (NO) triggers the formation of SGs. Whereas the composition of NO-induced SGs is initially similar to sodium arsenite (SA)-induced type I (cytoprotective) SGs, the progressive loss of eIF3 over time converts them into pro-death (type II) SGs. NO-induced SG assembly requires the phosphorylation of eIF2α, but the transition to type II SGs is temporally linked to the mTOR-regulated displacement of eIF4F complexes from the m⁷ guanine cap. Whereas SA does not affect mitochondrial morphology or function, NO alters mitochondrial integrity and function, resulting in increased ROS production, decreased cytoplasmic ATP, and plasma membrane permeabilization, all of which are supported by type II SG assembly. Thus, cellular energy balance is linked to the composition and function of NO-induced SGs in ways that determine whether cells live or die.

Protective Effects of N-Acetyl-L-Cysteine on the Density of Spiral Ganglion Cells and Histological Changes Induced by Continuous Noise Exposure in Rats

BACKGROUND

Noise exposure causes loss of cochlea hair cells, leading to permanent sensorineural hearing loss, and initiates pathological changes to the bipolar primary auditory neurons (ANs). This study focuses on the effects of N-acetyl-l-cysteine (NAC) in protecting the density of spiral ganglion cells and in histological changes induced by continuous noise exposure in rats.

METHODS

Twenty-four male Wistar rats were randomly allocated into four experimental groups to receive NAC, saline, noise, or both noise and NAC. Noise exposure continued for ten days. Saline and NAC were injected daily during the noise exposure, and 2 days before and after the noise exposure. Evaluation of cochlear histopathology and the density of spiral ganglion cells was performed 21 days after exposure.

RESULTS

In the animals exposed to noise, a reduction in the density of spiral ganglion cells was evident in both the basal and middle turns of the cochlea. This improved on receiving NAC treatment (P = 0.046). In the histopathology evaluation, some histological changes, such as disorganised architecture of the outer hair and supporting cells and a slightly thickened basilar membrane, were found in the basal turns in the noise group.

CONCLUSION

NAC offered partial protection against noise exposure by improving the density of spiral ganglion cells and reducing morphological changes.

Detection of dinitrosyl iron complexes by ozone-based chemiluminescence

Dinitrosyl iron complexes (DNICs) are important intermediates in the metabolism of nitric oxide (NO). They have been considered to be NO storage adducts able to release NO, scavengers of excess NO during inflammatory hypotensive shock, and mediators of apoptosis in cancer cells, among many other functions. Currently, all studies of DNICs in biological matrices use electron paramagnetic resonance (EPR) for both detection and quantification. EPR is limited, however, by its ability to detect only paramagnetic mononuclear DNICs even though EPR-silent binuclear are likely to be prevalent. Furthermore, physiological concentrations of mononuclear DNICs are usually lower than the EPR detection limit (1 μM). We have thus developed a chemiluminescence-based method for the selective detection of both DNIC forms at physiological, pathophysiological, and pharmacologic conditions. We have also demonstrated the use of the new method in detecting DNIC formation in the presence of nitrite and nitrosothiols within biological fluids and tissue. This new method, which can be used alone or in tandem with EPR, has the potential to offer insight about the involvement of DNICs in many NO-dependent pathways.

N-Acetyl-L-Cysteine Protects Liver and Kidney Against Chromium(VI)-Induced Oxidative Stress in Mice

Acute hexavalent chromium [Cr(VI)] compound exposure may lead to hepatotoxic and nephrotoxic effects. Cr(VI) reduction may generate reactive intermediates and radicals which might be associated with damage. We investigated effects of N-acetyl-l-cysteine (NAC) pre- or post-treatment on oxidative stress and accumulation of Cr in liver and kidney of Cr(VI)-exposed mice. Intraperitoneal potassium dichromate injection (20 mg Cr/kg) caused a significant elevation of lipid peroxidation in both tissues as compared to control (p < 0.05). Significant decreases in non-protein sulfhydryl (NPSH) level, as well as enzyme activities of catalase (CAT) and superoxide dismutase (SOD) along with significant accumulation of Cr in the tissues (p < 0.05) were of note. NAC pre-treatment (200 mg/kg, ip) provided a noticeable alleviation of lipid peroxidation (p < 0.05) in both tissues, whereas post-treatment exerted significant effect only in kidney. Similarly, Cr(VI)-induced NPSH decline was restored by NAC pre-treatment in both tissues (p < 0.05); however, NAC post-treatment could only replenish NPSH in liver (p < 0.05). Regarding enzyme activities, in liver tissue NAC pre-treatment provided significant restoration on Cr(VI)-induced CAT inhibition (p < 0.05), while SOD enzyme activity was regulated to some extent. In kidney, SOD activity was efficiently restored by both treatments (p < 0.05), whereas CAT enzyme alteration could not be totally relieved. Additionally, NAC pre-treatment in both tissues and post-treatment in liver exerted significant tissue Cr level decreases (p < 0.05). Overall, especially NAC pre-treatment seems to provide beneficial effects in regulating pro-oxidant/antioxidant balance and Cr accumulation caused by Cr(VI) in liver and kidney. This finding may be due to several mechanisms including extracellular reduction or chelation of Cr(VI) by readily available NAC.

N-Acetylcysteine's Role in Sepsis and Potential Benefit in Patients With Microcirculatory Derangements

OBJECTIVE

To review the data surrounding the utility of N-acetylcysteine (NAC) in sepsis and identify areas needed for additional research.

DATA SOURCES

A review of articles describing the mechanisms of action and clinical use of NAC in sepsis.

SUMMARY OF REVIEW

Despite many advances in critical care medicine, still as many as 50% of patients with septic shock die. Treatments thus far have focused on resuscitation and restoration of macrocirculatory targets in the early phases of sepsis, with less focus on microcirculatory dysfunction. N-acetylcysteine, due to its anti-inflammatory and antioxidative properties, has been readily investigated in sepsis and has yielded largely incongruous and disappointing results. In addition to its known anti-inflammatory and antioxidative roles, one underappreciated property of NAC is its ability to vasodilate the microcirculation and improve locoregional blood flow. Some investigators have sought to capitalize on this mechanism with promising results, as evidenced by microcirculatory vasodilation, improvements in regional blood flow and oxygen delivery, and reductions in lactic acidosis, organ failure, and mortality.

CONCLUSION

In addition to its antioxidant and anti-inflammatory properties, N-acetylcysteine possesses vasodilatory properties that could benefit the microcirculation in sepsis. It is imperative that we investigate these properties to uncover NAC's full potential for benefit in sepsis.

Thymoquinone mitigate ischemia-reperfusion-induced liver injury in rats: a pivotal role of nitric oxide signaling pathway

Oxidative and nitrosative stress-induced endothelial cell damage play an essential role in the pathogenesis of hepatic ischemia-reperfusion (IR) injury. IR is associated with reduced eNOS expression and exacerbated by superimposed stress. NOSTRIN induces intracellular endothelial nitric oxide synthase (eNOS) translocation and inducible nitric oxide synthase (iNOS) increases nitric oxide (NO) production. Our aim was to assess hepatic expression of iNOS, eNOS, and NOSTRIN in IR with or without N-acetylcysteine (NAC) or thymoquinone (TQ) pretreatment and to compare their hepatoprotective effects. Surgical induction of IR was performed by occlusion of hepatic pedicle for 30 min with mini-clamp and reperfused for 30 min. The effects of TQ (20 mg/kg/day) or NAC (300 mg/kg/day) administered orally for 10 days were evaluated by serum ALT and AST, oxidative stress parameters, NO production, and histopathological analysis. Also, localization and expression of iNOS, eNOS, and NOSTRIN were assessed by immunofluorescence. TQ or NAC pretreatment significantly decreased elevated serum aspartate aminotransferase (AST), alanine aminotransferase (ALT), and myeloperoxidase (MPO) activities, malondialdehyde (MDA) level, and NO production. In addition, they restored the depleted GSH content and alleviated histopathological changes. Furthermore, they up-regulated eNOS and down-regulated iNOS and NOSTRIN expressions. TQ exerts its hepatoprotective effect, at least in part, by nitric oxide signaling pathway through modulation of iNOS, eNOS, and NOSTRIN expressions as well as suppression of oxidative stress.

Oxidative Stress and Lung Ischemia-Reperfusion Injury

Ischemia-reperfusion (IR) injury is directly related to the formation of reactive oxygen species (ROS), endothelial cell injury, increased vascular permeability, and the activation of neutrophils and platelets, cytokines, and the complement system. Several studies have confirmed the destructiveness of the toxic oxygen metabolites produced and their role in the pathophysiology of different processes, such as oxygen poisoning, inflammation, and ischemic injury. Due to the different degrees of tissue damage resulting from the process of ischemia and subsequent reperfusion, several studies in animal models have focused on the prevention of IR injury and methods of lung protection. Lung IR injury has clinical relevance in the setting of lung transplantation and cardiopulmonary bypass, for which the consequences of IR injury may be devastating in critically ill patients.

Protective effect of N-acetylcysteine (NAC) on renal ischemia/reperfusion injury through Nrf2 signaling pathway

The aim of this study was to investigate whether N-acetylcysteine (NAC), a known antioxidant, can protect kidney against ischemic injury through regulating Nrf2 signaling pathway. The expression of Nrf2, HO-1 and cleaved caspase 3 were analyzed by Western blot analysis. Apoptosis of renal tubular epithelial cells was assessed by the TUNEL method. Malondialdehyde (MDA) levels were measured by the thiobarbituric acid reaction. Blood serum creatinine and blood urea nitrogen levels were measured with an Olympus automatic multi-analyzer. We found that NAC significantly increased Nrf2 and downstream HO-1 expression. Furthermore, NAC significantly decreased cleaved caspase 3, p53 and renal epithelial tubular cell apoptosis. In addition, NAC reduced the MDA level. These findings suggest that the protective action of NAC on ischemia renal injury is associated closely with Nrf2 signaling pathway.

Effect of N-acetylcysteine on the spinal-cord glutathione system and nitric-oxide metabolites in rats with neuropathic pain

Since N-acetylcysteine (NAC) is a donor of cysteine, we studied the relationship between NAC and concentration of oxidized and reduced glutathione (GSH/GSSG ratio), and glutathione peroxidase (GPx) and glutathione-S-transferase (GST) activities in the lumbosacral spinal cord of rats with chronic constriction injury (CCI) of the sciatic nerve that received NAC (150mg/kg/day, i.p.) or 0.9% saline solution for 3 or 10 days. Hydrogen peroxide (H2O2) and nitric-oxide (NO) metabolites were also measured. Von Frey hair and hot-plate tests showed hyperalgesia at day 1 in CCI rats. Hyperalgesia persisted at all other times in saline-treated CCI rats, but returned to pre-injury values in NAC-treated CCI rats after 3 postoperative days. GST activity and the GSH/GSSG ratio increased in saline-treated CCI rats, while the NAC treatment increased GST and GPx activities at day 10, with no significant change in the GSH/GSSG ratio. NAC treatment did not affect H2O2 levels, but it reduced NO metabolites in CCI rats 3 days after the surgery. Thus, the anti-hyperalgesic effect of NAC appears not to involve its action as a cysteine precursor for GSH synthesis, but involves a decrease in NO.

Dietary antioxidants prevent alcohol-induced ciliary dysfunction

Previously we have shown that chronic alcohol intake causes alcohol-induced ciliary dysfunction (AICD), leading to non-responsive airway cilia. AICD likely occurs through the downregulation of nitric oxide (NO) and cyclic nucleotide-dependent kinases, protein kinase G (PKG) and protein kinase A (PKA). Studies by others have shown that dietary supplementation with the antioxidants N-acetylcysteine (NAC) and procysteine prevent other alcohol-induced lung complications. This led us to hypothesize that dietary supplementation with NAC or procysteine prevents AICD. To test this hypothesis, C57BL/6 mice drank an alcohol/water solution (20% w/v) ad libitum for 6 weeks and were concurrently fed dietary supplements of either NAC or procysteine. Ciliary beat frequency (CBF) was measured in mice tracheas, and PKG/PKA responsiveness to β-agonists and NOx levels were measured from bronchoalveolar lavage (BAL) fluid. Long-term alcohol drinking reduced CBF, PKG and PKA responsiveness to β-agonists, and lung NOx levels in BAL fluid. In contrast, alcohol-drinking mice fed NAC or procysteine sustained ciliary function and PKG and PKA responsiveness to β-agonists. However, BAL NO levels remained low despite antioxidant supplementation. We also determined that removal of alcohol from the drinking water for as little as 1 week restored ciliary function, but not PKG and PKA responsiveness to β-agonists. We conclude that dietary supplementation with NAC or procysteine protects against AICD. In addition, alcohol removal for 1 week restores cilia function independent of PKG and PKA activity. Our findings provide a rationale for the use of antioxidants to prevent damage to airway mucociliary functions in chronic alcohol-drinking individuals.

Reestablishment of ischemia-reperfusion liver injury by N-acetylcysteine administration prior to a preconditioning iron protocol

The role of iron (Fe)-induced prooxidant status in Fe preconditioning against ischemia (1 h)-reperfusion (20 h) induced liver injury was assessed using N-acetylcysteine (NAC) (1 g/kg) before Fe (50 mg/kg), given to male Sprague Dawley rats on alternate days during 10 days. IR significantly increased serum aspartate transaminase (AST) and alanine transaminase (ALT) levels, with drastic changes in liver histology, hepatic glutathione depletion, and nuclear factor-κB (NF-κB) p65 diminution (P < 0.05) (ELISA). Fe-induced liver oxidative stress, as evidenced by higher protein carbonyl/glutathione content ratios (P < 0.05) at days 11 and 12 after treatment, was abolished by NAC. Under these conditions, short-term Fe administration exerted significant protection against IR liver injury, as shown by 85% and 60% decreases in IR-induced serum AST and ALT (P < 0.05), respectively, and normalization of hepatic histology, glutathione levels, and NF-κB activation, changes that were suppressed by NAC administration prior to Fe. Results of this study indicate that NAC administration prior to an iron protocol reestablishes IR liver injury, supporting the role of Fe-induced transient oxidative stress in hepatoprotection and its potential clinical application.

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.

N-acetylcysteine improves redox status, mitochondrial dysfunction, mucin-depleted crypts and epithelial hyperplasia in dextran sulfate sodium-induced oxidative colitis in mice

The effect of N-acetylcysteine (NAC), a pharmacological antioxidant was investigated in a murine model of chronic colitis. Male NMRI mice were given 5% dextran sulfate sodium (DSS) in drinking water for 5 days followed by 10 days of water, three times. Compared to control mice given water, DSS-treated mice displayed severe imbalanced redox status with decreased glutathione and catalase, but increased malondialdehyde, protein carbonyls, nitric oxide and myeloperoxidase levels, at days 35th (active colitis) and 45th (recovery period). It also resulted in mitochondrial dysfunction, mucosal ulcers, mucin-depleted crypts and epithelial cell apoptosis. Crypt abscesses and glandular hyperplasia occurred selectively in distal colon. NAC (150 mg/kg) given in drinking water for 45 days along with 3 DSS cycles improved the hallmarks of DSS-colitis. Interestingly, the moderate impact of NAC on lipids and proteins oxidation correlated with myeloperoxidase and nitric oxide levels.NAC as a mucoregulator and a thiol restoring agent is protective on oxidative crypt alterations, mucin depletion, epithelial cell hyperplasia and apoptosis. Taken together, our results highlight the role of NAC as a scavenger of phagocytes-derived reactive oxygen species in mice DDS-colitis, suggesting that a long term NAC diet might be beneficial in inflammatory bowel diseases and colorectal cancer.

Interleukin-13/-4-induced oxidative stress contributes to death of hippocampal neurons in aβ1-42-treated hippocampus in vivo

AIMS

The present study examined whether Aβ(1-42) can induce endogenous expression of interleukin-13 (IL-13) or (IL-4) within activated microglia in the rat hippocampus in vivo. We further investigated whether these cytokines mediate ROS/RNS generation through activation of NADPH oxidase and/or inducible nitric oxide synthase (iNOS), and thus contribute to the degeneration of hippocampal neurons in vivo.

RESULTS

Here, we show that IL-13 and IL-4, endogenously expressed in Aβ(1-42)-activated microglia in hippocampus in vivo, contribute to degeneration of hippocampal neurons in vivo. Neutralization of IL-13 and IL-4 protected hippocampal neurons in vivo against neurotoxicity by inhibiting activation of microglial NADPH oxidase and iNOS, resulting in attenuation of ROS generation and oxidative damage of protein, lipid and DNA.

INNOVATION

To our knowledge, this is the first study to demonstrate the possible involvement of endogenously expressed IL-13 and/or IL-4 in activated microglia after Aβ(1-42) injection in the degeneration of hippocampal neurons in vivo. The current findings suggest that the deleterious effects of microglia-derived endogenous IL-13 and/or IL-4 are involved in oxidative stress-mediated neurodegenerative diseases, such as AD.

CONCLUSION

We carefully hypothesize that IL-13 and IL-4, well-known as anti-inflammatory cytokines might serve as neurotoxic mediators by enhancing microglia-derived oxidative stress in Aβ(1-42)-treated hippocampus in vivo.

N-acetylcysteine attenuates copper overload-induced oxidative injury in brain of rat

Copper is an integral part of many important enzymes involved in a number of vital biological processes. Even though it is essential to life, at elevated tissue concentrations, copper can become toxic to cells. Recent studies have reported oxidative damage due to copper in various tissues. Considering the vulnerability of the brain to oxidative stress, this study was undertaken to explore possible beneficial antioxidant effects of N-acetylcysteine on oxidative stress induced by copper overload in brain tissue of rats. Thirty-two Wistar rats were equally divided into four groups. The first group was used as control. The second, third, and fourth groups were given 1 g/L copper in their drinking water for 1 month. At the end of this period, the group 2 rats were sacrificed. During the next 2 weeks, the rats in group 3 were injected intraperitoneally with physiological saline and those in group 4 with 20 mg/kg intraperitoneal injections of N-acetylcysteine. In group 2 the lipid peroxidation and nitric oxide levels were increased in the brain cortex while the activities of superoxide dismutase and catalase and the concentration of glutathione were decreased. In rats treated with N-acetylcysteine, lipid peroxidation decreased and the activities of antioxidant enzyme improved in the brain cortex. In conclusion, treatment with N-acetylcysteine modulated the antioxidant redox system and reduced brain oxidative stress induced by copper.

Inhibition of germinal vesicle breakdown by antioxidants and the roles of signaling pathways related to nitric oxide and cGMP during meiotic resumption in oocytes of a marine worm

In mammalian oocytes, cAMP elevations prevent the resumption of meiotic maturation and thereby block nuclear disassembly (germinal vesicle breakdown (GVBD)), whereas nitric oxide (NO) and its downstream mediator cGMP can either inhibit or induce GVBD. Alternatively, some invertebrate oocytes use cAMP to stimulate, rather than inhibit, GVBD, and in such cases, the effects of NO/cGMP signaling on GVBD remain unknown. Moreover, potential interactions between NO/cGMP and AMP-activated kinase (AMPK) have not been assessed during GVBD. Thus, this study analyzed intraoocytic signaling pathways related to NO/cGMP in a marine nemertean worm that uses cAMP to induce GVBD. For such tests, follicle-free nemertean oocytes were stimulated to mature by seawater (SW) and cAMP elevators. Based on immunoblots and NO assays of maturing oocytes, SW triggered AMPK deactivation, NO synthase (NOS) phosphorylation, and an NO elevation. Accordingly, SW-induced GVBD was blocked by treatments involving the AMPK agonist AICAR, antioxidants, the NO scavenger carboxy-PTIO, NOS inhibitors, and cGMP antagonists that target the NO-stimulated enzyme, soluble guanylate cyclase (sGC). Conversely, SW solutions combining NO/cGMP antagonists with a cAMP elevator restored GVBD. Similarly, AICAR plus a cAMP-elevating drug reestablished GVBD while deactivating AMPK and phosphorylating NOS. Furthermore, sGC stimulators and 8-Br-cGMP triggered GVBD. Such novel results indicate that NO/cGMP signaling can upregulate SW-induced GVBD and that cAMP-elevating drugs restore GVBD by overriding the inhibition of various NO/cGMP downregulators, including AMPK. Moreover, considering the opposite effects of intraoocytic cAMP in nemerteans vs mammals, these data coincide with previous reports that NO/cGMP signaling blocks GVBD in rats.

N-Acetylcysteine prevents baker's-yeast-induced inflammation and fever

OBJECTIVE AND DESIGN

To investigate whether N-acetylcysteine (NAC) alters baker's-yeast-induced fever and inflammation.

MATERIAL OR SUBJECTS

Male Wistar rats (26-28 days old) injected with baker's yeast (135 mg/kg, intraperitoneal) or prostaglandin E(2) (300 ng/100 μL, intrathecal).

TREATMENT

Rats were injected with NAC (500 mg/kg, subcutaneous, or 50 μg/100 μL, intrathecal) 1 h before, or 2 h after, pyrogen injection.

METHODS

Rectal temperature changes induced by baker's yeast, PGE(2) and NAC were followed up over time. Four hours after baker's yeast injection, total leukocytes, protein, interleukin (IL)-1β, tumor necrosis factor (TNF)-α and nonprotein thiol content were assessed in peritoneal lavage and hypothalamus.

RESULTS

Systemic administration of NAC decreased leukocytes, protein, IL-1β and TNF-α levels in peritoneal lavage, and decreased IL-1β levels in the hypothalamus. The central administration of NAC prevented baker's-yeast-induced fever, but did not alter the febrile response elicited by prostaglandin E(2).

CONCLUSION

These results suggest an anti-inflammatory and antipyretic role for NAC in yeast-induced peritonitis.

A novel parthenin analog exhibits anti-cancer activity: activation of apoptotic signaling events through robust NO formation in human leukemia HL-60 cells

This study describes the anti-cancer activity of P19, an analog of parthenin. P19 induced apoptosis in HL-60 cells and inhibited cell proliferation with 48h IC50 of 3.5μM. At 10mg/kg dose, it doubled the median survival time of L1210 leukemic mice and at 25mg/kg it inhibited Ehrlich ascites tumor growth by 60%. Investigation of the mechanism of P19 induced apoptosis in HL-60 cells revealed that N-acetyl-l-cysteine (NAC) and s-methylisothiourea (sMIT) could reverse several molecular events that lead to cell death by inhibiting nitric oxide (NO) formation. It selectively produced massive NO in cells while quenching the basal ROS levels with concurrent elevation of GSH. P19 disrupted mitochondrial integrity leading to cytochrome c release and caspase-9 activation. P19 also caused caspase-8 activation by selectively elevating the expression of DR4 and DR5. All these events lead to the activation of caspase-3 leading to PARP-1 cleavage and DNA fragmentation. However, knocking down of AIF by siRNA also suppressed the apoptosis substantially thus indicating caspase independent apoptosis, too. Further, contrary to enhanced iNOS expression, its transcription factor, NF-κB (p65) was cleaved with a simultaneous increase in cytosolic IκB-alpha. In addition, P19 potently inhibited pro-survival proteins pSTAT3 and survivin. The multi-modal pro-apoptotic activity of P19 raises its potential usefulness as a promising anti-cancer therapeutic.

Japanese encephalitis virus-infected macrophages induce neuronal death

Inflammation in the central nervous system (CNS) in Japanese encephalitis (JE) is shown to be the result of microglial activation that leads to the release of various proinflammatory mediators. Peripheral macrophages have been reported to infiltrate into the CNS in JE, though their contribution to the inflammatory process is yet to be elucidated. In this study, using an in vitro macrophage model, we have shown that upon JE virus infection, these cells secrete various soluble factors which may significantly add to the existing inflammatory milieu and lead to apoptotic or necrotic death of neurons. However, it is difficult to quantify the extent of involvement of either the microglia or infiltrating macrophages in the inflammatory processes.

Impairment of 8-iso-PGF(2ALPHA) isoprostane metabolism by dietary conjugated linoleic acid (CLA)

8-iso-PGF(2alpha) isoprostane (IP) is one of the most-used markers of lipid peroxidation in experimental models and humans. After its formation, it is promptly metabolized to 2,3 dinor (DIN) in peroxisomes. Conjugated linoleic acid (CLA) is preferentially beta-oxidized in peroxisomes which may compete with IP, and thereby may affect its metabolism. In order to verify whether CLA is able to influence IP formation and/or metabolism and to explain the mechanism, we challenged rats supplemented with CLA or with triolein (as a control fatty acid), with a single dose of carbon tetrachloride (CCl(4)) or of bacterial lipopolysaccharide (LPS). The results showed that IP and its precursor arachidonic acid hydroperoxide, as well as malondialdehyde (MDA), increase significantly in the liver of rats challenged with CCl(4), irrespective of the diet, while in LPS-treated rats only nitrites in liver and isoprostane in plasma increase. On the other hand, the peroxisomal beta-oxidation products of IP, the DIN, is significantly lower in the CLA group with respect to control and triolein groups. To further investigate whether this is due to competition between CLA and IP at the cellular level, we incubated human fibroblasts from healthy subjects or patients with adrenoleukodystrophy (ALD), with CLA and/or commercially available IP. The rationale of this approach is based on the deficient peroxisomal beta-oxidation of fibroblasts from ALD patients, leading to a reduced formation of DIN. In both normal and ALD cells, the presence of CLA significantly inhibits the formation of DIN from IP. We may conclude that both in vitro and in vivo studies strongly suggest that CLA may impair IP catabolism in peroxisomes. Consequently an increase of IP, as a sole result of CLA intake, cannot be considered as a marker of lipid peroxidation.

Intestinal barrier function in response to abundant or depleted mucosal glutathione in Salmonella-infected rats

Background

Glutathione, the main antioxidant of intestinal epithelial cells, is suggested to play an important role in gut barrier function and prevention of inflammation-related oxidative damage as induced by acute bacterial infection. Most studies on intestinal glutathione focus on oxidative stress reduction without considering functional disease outcome. Our aim was to determine whether depletion or maintenance of intestinal glutathione changes susceptibility of rats to Salmonella infection and associated inflammation.

Rats were fed a control diet or the same diet supplemented with buthionine sulfoximine (BSO; glutathione depletion) or cystine (glutathione maintenance). Inert chromium ethylenediamine-tetraacetic acid (CrEDTA) was added to the diets to quantify intestinal permeability. At day 4 after oral gavage with Salmonella enteritidis (or saline for non-infected controls), Salmonella translocation was determined by culturing extra-intestinal organs. Liver and ileal mucosa were collected for analyses of glutathione, inflammation markers and oxidative damage. Faeces was collected to quantify diarrhoea.

Results

Glutathione depletion aggravated ileal inflammation after infection as indicated by increased levels of mucosal myeloperoxidase and interleukin-1β. Remarkably, intestinal permeability and Salmonella translocation were not increased. Cystine supplementation maintained glutathione in the intestinal mucosa but inflammation and oxidative damage were not diminished. Nevertheless, cystine reduced intestinal permeability and Salmonella translocation.

Conclusion

Despite increased infection-induced mucosal inflammation upon glutathione depletion, this tripeptide does not play a role in intestinal permeability, bacterial translocation and diarrhoea. On the other hand, cystine enhances gut barrier function by a mechanism unlikely to be related to glutathione.

Effects of postresuscitation N-acetylcysteine on cerebral free radical production and perfusion during reoxygenation of hypoxic newborn piglets

Hydrogen peroxide (H2O2) and nitric oxide (NO) contribute to the pathogenesis of cerebral hypoxic-ischemic injury. We evaluated the neuroprotective effect of N-acetyl-l-cysteine (NAC, a free radical scavenger) against oxidative stress and perfusion in a model of neonatal hypoxia-reoxygenation (H-R). Piglets (1-3 d, 1.6-2.3 kg) were randomized into a sham-operated group (without H-R) (n = 5) and two H-R experimental groups (2 h normocapnic alveolar hypoxia followed by 4 h reoxygenation) (n = 7/group). Five minutes after reoxygenation, piglets were given either i.v. saline (H-R controls) or NAC (30 mg/kg bolus then 20 mg/kg/h infusion) in a blinded-randomized fashion. Heart rate, mean arterial pressure, carotid arterial blood flow (transit-time ultrasonic probe), cerebral cortical H2O2 and NO production (electrochemical sensor), cerebral tissue glutathione and nitrotyrosine levels (enzyme-linked immunosorbent assay) were examined. Hypoxic piglets were acidotic (pH 6.88-6.90), which recovered similarly in the H-R groups (p > 0.05 versus shams). Postresuscitation NAC treatment significantly attenuated the increase in cortical H2O2, but not NO, concentration during reoxygenation, with lower cerebral oxidized glutathione levels. NAC-treated piglets had significantly higher carotid oxygen delivery and lower cerebral lactate levels than that of H-R controls with corresponding changes in carotid arterial flow and vascular resistance. In newborn piglets with H-R, postresuscitation administration of NAC reduced cerebral oxidative stress and improved cerebral perfusion.

Effect OfN-Acetylcysteine on Carboplatin-Induced Ototoxicity and Nitric Oxide Levels in a Rat Model

OBJECTIVE

The aim of the present study is to investigate the effect of N-acetylcysteine (NAC) given 30 minutes before carboplatin administration on carboplatin-induced ototoxicity and nitric oxide (NO) levels in a rat model.

STUDY DESIGN

Animal study.

METHODS

Eighteen Sprague-Dawley rats were divided into three groups that each contained six animals. Intraperitoneal injection of physiologic saline was performed in group 1 twice with an interval of 30 minutes. Group 2 was treated with a single bolus administration of carboplatin at a dose of 256 mg/kg 30 minutes after the intraperitoneal injection of physiologic saline. Group 3 was treated with a single bolus administration of carboplatin at a dose of 256 mg/kg 30 minutes after the intraperitoneal injection of NAC at a dose of 400 mg/kg. Pretreatment and posttreatment distortion product otoacoustic emissions (DPOAE) were performed in rats from all groups. Then, the animals were sacrificed on the fourth day, and cochlear tissue NO and glutathione peroxidase (GSH-Px) levels were measured.

RESULTS

The comparison of pre- and posttreatment DPOAE responses did not demonstrate any significant changes for groups 1 and 3. Results of group 2 showed a decrease of the DPOAE amplitude. Cochlear NO levels were significantly higher in rats treated with carboplatin than in controls and in those treated with carboplatin plus NAC (P < .05). Cochlear GSH-Px levels were higher in rats treated with carboplatin plus NAC than in those treated with carboplatin, but the difference did not reach statistical significance (P = .079).

CONCLUSIONS

The present study showed that carboplatin at higher doses induced hearing loss and increased NO levels in the cochlea of rats. NAC appears to have a protective effect against carboplatin-induced ototoxicity, which may be related to its inhibitory effect on NO production.

N-acetylcysteine for patients with prolonged hypotension as prophylaxis for acute renal failure (NEPHRON)

BACKGROUND

Acute renal failure is a common complication in critically ill patients and carries an increased morbidity and mortality. N-acetylcysteine is an antioxidant and anti-inflammatory agent that may counteract some of the pathophysiologic derangements in shock states.

OBJECTIVE

To test whether the administration of N-acetylcysteine, compared with placebo, reduces the incidence of acute renal failure in hypotensive patients.

DESIGN

Prospective, randomized, double-blinded, placebo-controlled study.

SETTING

Intensive care units of a university tertiary care hospital.

PATIENTS

One hundred forty-two patients with new onset (within 12 hrs) of at least>or=30 consecutive minutes of hypotension and/or vasopressor requirement.

INTERVENTIONS

Patients were randomized to receive either N-acetylcysteine or placebo for 7 days, in addition to standard supportive therapy.

MEASUREMENTS AND MAIN RESULTS

Patients who received N-acetylcysteine had an incidence of acute renal failure (>or=0.5 mg/dL increase in creatinine) of 15.5%, compared with 16.9% in those receiving placebo (p=.82, not significant). There were no significant differences between treatment arms in any of the secondary outcomes examined, including incidence of a 50% increase in creatinine, maximal rise in creatinine, recovery of renal function, length of intensive care unit and hospital stay, requirement for renal replacement therapy, and mortality. Among patients receiving N-acetylcysteine, there were trends toward reduced incidence of acute renal failure in patients with baseline Sequential Organ Failure Assessment (SOFA) score>8 (p=.12), lower SOFA scores during the first 4 days of treatment (p=.28), and reduced mortality in patients<65 yrs of age (p=.20).

CONCLUSIONS

There were no significant differences in any of our primary or secondary end points between patients treated with N-acetylcysteine or placebo. Trends toward reduced incidence of acute renal failure in patients with baseline SOFA score >8, reduced SOFA scores during the first 4 days, and reduced mortality in patients<65 yrs of age are provocative but require further study to determine their clinical significance.

N-acetylcysteine prevents nitrosative stress-associated depression of blood pressure and heart rate in streptozotocin diabetic rats

Previous studies have indicated that cardiovascular abnormalities such as depressed blood pressure and heart rate occur in streptozotocin (STZ) diabetic rats. Chronic diabetes, which is associated with increased expression of inducible nitric oxide synthase (iNOS) and oxidative stress, may produce peroxynitrite/nitrotyrosine and cause nitrosative stress. We hypothesized that nitrosative stress causes cardiovascular depression in STZ diabetic rats and therefore can be corrected by reducing its formation. Control and STZ diabetic rats were treated orally for 9 weeks with N-acetylcysteine (NAC), an antioxidant and inhibitor of iNOS. At termination, the mean arterial blood pressure (MABP) and heart rate (HR) were measured in conscious rats. Nitrotyrosine and endothelial nitric oxide synthase (eNOS) and iNOS expression were assessed in the heart and mesenteric arteries by immunohistochemistry and Western blot experiments. Untreated diabetic rats showed depressed MABP and HR that was prevented by treatment with NAC. In untreated diabetic rats, levels of 15-F(2t)-isoprostane, an indicator of lipid peroxidation increased, whereas plasma nitric oxide and antioxidant concentrations decreased. Furthermore, decreased eNOS and increased iNOS expression were associated with elevated nitrosative stress in blood vessel and heart tissue of untreated diabetic rats. N-acetylcysteine treatment of diabetic rats not only restored the antioxidant capacity but also reduced the expression of iNOS and nitrotyrosine and normalized the expression of eNOS to that of control rats in heart and superior mesenteric arteries. The results suggest that nitrosative stress depress MABP and HR following diabetes. Further studies are required to elucidate the mechanisms involved in nitrosative stress mediated depression of blood pressure and heart rate.

Antioxidant N-acetylcysteine restores systemic nitric oxide availability and corrects depressions in arterial blood pressure and heart rate in diabetic rats

Increased oxidative stress and reduced nitric oxide (NO) bioactivity are key features of diabetes mellitus that eventually result in cardiovascular abnormalities. We assessed whether N-acetylcysteine (NAC), an antioxidant and glutathione precursor, could prevent the hyperglycaemia induced increase in oxidative stress, restore NO availability and prevent depression of arterial blood pressure and heart rate in vivo in experimental diabetes. Control (C) and streptozotocin-induced diabetic (D) rats were treated or not treated with NAC in drinking water for 8 weeks, initiated 1 week after induction of diabetes. At termination, plasma levels of free 15-F2t-isoprostane, a specific marker of oxygen free radical induced lipid peroxidation, was increased while the plasma total antioxidant concentration was decreased in untreated diabetic rats as compared to control rats (P<0.05). This was accompanied by a significant reduction of plasma levels of nitrate and nitrite, stable metabolites of NO, (P<0.05, D vs. C) and a reduced endothelial NO synthase protein expression in the heart and in aortic and mesenteric artery tissues. Systolic, diastolic and mean arterial blood pressures (SBP, DBP and MAP) and heart rate (HR) were reduced in diabetic rats (P<0.05 vs. C) and NAC normalised the changes that occurred in the diabetic rats. The protective effects may be attributable to restoration of NO bioavailability in the circulation.

N -acetylcysteine and S -methylcysteine inhibit MeIQx rat hepatocarcinogenesis in the post-initiation stage

N-acetylcysteine (NAC) and S-methylcysteine (SMC), water soluble organosulfur compounds contained in garlic, were evaluated for chemoprevention of hepatocarcinogenesis after 2-amino-3,8-dimethylimidazo[4,5-f]quinoxaline (MeIQx) initiation in rats. Intergastric treatment with NAC or SMC five times a week resulted in decreased numbers and areas of preneoplastic, glutathione S-transferase placental form (GST-P) positive foci of the liver in a dose-dependent manner. Moreover, cell proliferation was reduced in GST-P positive foci by NAC and SMC. Insulin-like growth factor I (IGF-I) and inducible nitric oxide synthase (iNOS) mRNA expressions were found downregulated in the liver by NAC. The studies indicate that NAC can serve as a chemopreventive agent for rat hepatocarcinogenesis induced by MeIQx by reducing cell proliferation, which may involve IGF-I and iNOS downregulation.

The effect of N-acetylcysteine on cardiac contractility to dobutamine in rats with streptozotocin-induced diabetes

We examined if myocardial depression at the acute phase of diabetes (3 weeks after injection of streptozotocin, 60 mg/kg i.v.) is due to activation of inducible nitric oxide synthase and production of peroxynitrite, and if treatment with N-acetylcysteine (1.2 g/day/kg for 3 weeks, antioxidant) improves cardiac function. Four groups of rats were used: control, N-acetylcysteine-treated control, diabetic and N-acetylcysteine-treated diabetic. Pentobarbital-anaesthetized diabetic rats, relative to the controls, had reduced left ventricular contractility to dobutamine (1-57 microg/min/kg). The diabetic rats also had increased myocardial levels of thiobarbituric acid reactive substances, immunostaining of inducible nitric oxide synthase and nitrotyrosine, and similar baseline 15-F2t-isoprostane. N-acetylcysteine did not affect responses in the control rats; but increased cardiac contractility to dobutamine, reduced myocardial immunostaining of inducible nitric oxide synthase and nitrotyrosine and level of 15-F2t-isoprostane, and increased cardiac contractility to dobutamine in the diabetic rats. Antioxidant supplementation in diabetes reduces oxidative stress and improves cardiac function.

Effects of erdosteine on smoking-induced lipid peroxidation in healthy smokers

AIM

Oxidative stress caused by smoking has been implicated in many pulmonary diseases. Smoking causes reductions in plasma nitrate plus nitrite (NOx) concentrations and increases in plasma malondialdehyde (MDA) concentrations, which indicate oxidative stress and lipid peroxidation, respectively. In this study, we investigated the acute effects of smoking a single cigarette on the plasma concentrations of NOx and thiobarbituric acid reactive substances (TBARS) including MDA, and whether administration of erdosteine, a mucolytic and antioxidant agent, affects these parameters.

METHODS

Thirty healthy smokers were included in the study. Subjects smoked a single cigarette in 10 minutes on the study day. For analysis of NOx, TBARS and cotinine, blood was drawn from each subject before and 5 and 30 minutes after smoking. The subjects were then randomly divided into two groups, one receiving placebo and the other erdosteine suspension 175mg/5mL twice daily for 1 month. After this treatment period, the same study protocol was carried out. Two subjects in the placebo and five subjects in the study group were excluded because of noncompliance.

RESULTS

Twenty-three (14 female, 9 male) subjects completed the study. Their mean age was 32 +/- 8 years and their smoking history was 14 +/- 9 pack-years. Baseline NOx, TBARS and cotinine concentrations were similar between the groups. NOx concentrations decreased significantly after smoke exposure. At the end of the treatment period there were no significant differences in NOx, TBARS or cotinine concentrations between the groups. The concentration of TBARS after smoking decreased significantly in the erdosteine-treated group (at 5 minutes: 2.8 +/- 0.5 micromol/L before treatment and 2.3 +/- 0.3 micromol/L after treatment, p < 0.05; at 30 minutes: 2.8 +/- 0.5 micromol/L before treatment and 1.8 +/- 0.7 micromol/L after treatment, p < 0.05). Smoking history was significantly correlated with cotinine concentrations.

CONCLUSION

Acute smoke exposure decreased plasma NOx concentrations in healthy smokers, and this was not changed with erdosteine treatment. However, significant decreases were noted in TBARS concentrations after smoke exposure in the group that received erdosteine, suggesting that short-term erdosteine administration might help prevent smoking-induced lipid peroxidation.

A combination of budesonide and the SH-metabolite I of erdosteine acts synergistically in reducing chemiluminescence during human neutrophil respiratory burst

Activated neutrophils can release superoxide anion and nitric oxide (NO), which subsequently combine with each other to yield peroxynitrite anions, powerful and harmful oxidants that preferentially mediate the oxidation of the thiol groups in proteins and non-protein molecules. These oxidants play a direct role in the inflammatory process in chronic obstructive pulmonary disease and asthma by increasing the number of neutrophils and macrophages that induce a self-sustaining phlogogenic loop. Budesonide (BUD) and erdosteine (a muco-active drug which, after metabolization, produces an active metabolite (Met I) with a sulfhydryl group) are both active in reducing the release of superoxide anion, NO and peroxynitrite, and can be administered to patients with respiratory diseases. The aim of this study was to investigate the possible synergistic in vitro effect of BUD and Met I on chemiluminescence generation during fMLP-stimulated respiratory bursts of human neutrophils with the NO donor L-arginine, added to the incubating medium. The investigated BUD concentrations ranged from 6 x 10(-8) to 1 x 10(-6) mol/l in logarithmic scale and a significant and progressive reduction in luminol-amplified chemiluminescence (LACL) was observed at concentrations ranging from 2.5 x 10(-7) to 1 x 10(-6) mol/l. The investigated concentrations of Met I varied from 0.62 to 10 microg/ml. No significant changes were observed at 0.62, 1.25, and 2.5 microg/ml, but a significant decrease in LACL was observed at 5 and 10 microg/ml. When the two drugs were combined, there was a greater significant decrease in LACL versus the single drugs with the combinations of BUD 1 x 10(-6) mol/l plus Met I 10 microg/ml, BUD 5 x 10(-7) mol/l plus Met I 5 microg/ml, BUD 2.5 x 10(-7) mol/l plus Met I 2.5 microg/ml, and BUD 1.25 x 10(-7) mol/l plus Met I 1.25 microg/ml. A further interesting finding was that the combination of BUD 2.5 x 10(-7) mol/l plus Met I 2.5 microg/ml and BUD 1.25 x 10(-7) mol/l plus Met I 1.25 microg/ml significantly decreased LACL, whereas the single concentrations had no significant effect, thus indicating the possibility of extending the duration of the effect. Our findings indicate a synergistic antioxidant effect when BUD and Met I are given together, which is of interest for counteracting the airway phlogosis involved in many respiratory diseases.

Effects of N-acetylcysteine on arginase, ornithine and nitric oxide in renal ischemia-reperfusion injury

BACKGROUND

Renal ischemia-reperfusion (I/R) is a complex syndrome involving several mechanisms such as renal vasoconstrictions, extensive tubular damage and glomerular injury. N-Acetylcysteine (NAC), a potent antioxidant by itself, may serve as a precursor for glutathione synthesis. The aim of this study was to investigate the possible effects of NAC on liver and kidney tissue arginase activity, ornithine and plasma nitric oxide levels during the I/R injury of kidney.

METHODS

Twenty-four female Sprague-Dawley rats divided into three groups: group 1; was given saline intraperitoneally (i.p.). Saline to group 2 and NAC (300 mg kg(-1)) to group 3 were injected i.p. 30 min before induction of ischemia. Groups 2 and 3; subjected to bilateral renal ischemia (60 min) followed by reperfusion (24 h). After the reperfusion period, the rats were sacrificed and liver and kidney tissue arginase activities, ornithine and plasma nitric oxide (NO) levels were determined.

RESULTS

NAC had an increasing effect on both of liver and kidney tissue arginase activities and ornithine levels while decreasing plasma NO concentration.

CONCLUSION

The stimulatory effect of NAC on arginase activity may result in an inhibition of the plasma NO level. Moreover, it could be possible that one of the protective mechanisms of NAC might be through the stimulation on the both liver and kidney tissue ornithine levels.

N-acetylcysteine prevents endotoxin-induced degeneration of oligodendrocyte progenitors and hypomyelination in developing rat brain

Periventricular leukomalacia (PVL), the dominant form of brain injury in premature infants, is characterized by diffuse white matter injury and is associated with cerebral palsy (CP). Maternal and placental infections are major causes of prematurity and identifiable etiology of PVL and CP. Here we have evaluated the therapeutic efficacy of N-acetylcysteine (NAC), a potent antioxidant and precursor of glutathione, to attenuate lipopolysaccharide (LPS)-induced white matter injury and hypomyelination in the developing rat brain, an animal model of PVL. Intraperitoneal pretreatment of pregnant female rats with NAC (50 mg/kg), 2 hr prior to administration of LPS at embryonic day 18 (E18), attenuated the LPS-induced expression of inflammatory cytokines such as tumor necrosis factor-alpha, interleukin-1beta, and inducible nitric oxide synthase in fetal rat brains. There were significantly reduced numbers of TUNEL(+) nuclei coimmunostained for platelet-derived growth factor-alphaR(+) [a surface marker for oligodendrocyte progenitor cells (OPCs)] at E20 in the subventricular zone of fetal rat brain in the NAC + LPS group compared with the untreated LPS group. Interestingly, immunostaining for O4 and O1 as markers for late OPCs and immature oligodendrocytes demonstrated fewer O4(+) and O1(+) cells in the LPS group compared with the NAC + LPS and control groups. Consistent with O4(+)/O1(+) cell counts, the expression of myelin proteins such as myelin basic protein, proteolipid protein, and 2'3'-cyclic nucleotide phosphodiesterase, including transcription factors such as MyT1 and Gtx, was less in the LPS group at late postnatal days, indicating severe hypomyelination in the developing rat brain when compared with NAC + LPS and control groups. Collectively, these data support the hypothesis that NAC may provide neuroprotection and attenuate the degeneration of OPCs against LPS evoked inflammatory response and white matter injury in developing rat brain. Moreover, these data suggest the possible use of NAC as a treatment for pregnant women with maternal or placental infection as a means of minimizing the risk of PVL and CP.

The effect of inducible nitric oxide synthase on postoperative adhesion formation in rats

OBJECTIVE

To evaluate the effect of iNOS on adhesion formation and to assess whether inhibition of iNOS expression affected adhesion formation according to adhesion maturation days.

STUDY DESIGN

Forty Wistar Albino rats were subjected to standardized lesion by cecal abrasion and parietal peritoneal defect and were randomly divided into four groups. Group I (control) received no treatment; groups II-IV received N-acetyl-cystein (NAC) 15 mg/100 g per day intramuscularly on days 4-14, 0-14 and 0-3, respectively, after surgery. On the postoperative 14th day adhesion score, tissue iNOS expression, inflammatory cell reaction (ICR) and tissue fibrosis score were determined.

RESULTS

Inflammation score of groups I and II was lower than that of groups III and IV (P < 0.05). Adhesion scores and tissue fibrosis of group II were significantly lower than that of the other groups (P < 0.001).

CONCLUSION

iNOS inhibition during the first 3 days postoperatively caused a delay in the resolution of inflammatory cell reaction. On the other hand, when inhibited after the first 3 days, adhesion formation and fibrosis were reduced both clinically and histopathologically.