Effectiveness of oral N -acetylcysteine in a rat experimental model of asthma

Development of spray-dried N-acetylcysteine dry powder for inhalation

N-acetylcysteine (NAC) has both antioxidant and immunomodulatory activities and has been used as adjuvant therapy in several viral infections. Recently, NAC attracted attention for its possible role in reducing the affinity of the spike protein receptor binding domain to angiotensin-converting enzyme (ACE2) receptors. Since only NAC solutions are available for inhalation, the purpose of the work was to develop a NAC dry powder for inhalation using mannitol or leucine as excipient. The powder was successfully produced using co-spray-drying with leucine. ATR-FTIR analyses evidenced spectral variations ascribed to the formation of specific interactions between NAC and leucine. This effect on the NAC environment was not evident for NAC-mannitol powders, but mannitol was in a different polymorphic form compared to the supplied material. Both the feedstock concentration and the leucine content have an impact on the powder aerodynamic features. In particular, to maximize the respirable fraction, it is preferable to produce the powder starting from a 0.5 % w/v feedstock solution using 33 to 50 % w/w leucine content. The NAC-leucine powder was stable for ten months maintaining NAC content of 50 % (w/w) and about 200 μg of NAC was able to deposit on a transwell insert, useful for future in vitro studies.

Immunomodulatory and anti-inflammatory effects of N-acetylcysteine in ovalbumin-sensitized rats

Background

Pro-inflammatory cytokines such as interleukin-5 (IL-5) and tumor necrosis factor-alpha (TNF-α) as well as immunoglobulin-E (IgE) appear to play a role in asthma. N-acetylcysteine (NAC), an antioxidant, might have clinical benefits in asthma prevention. The possible preventive effects of NAC against experimentally induced asthma in rats are investigated. The rats were allocated into five groups: a normal control, asthma control, a standard dexamethasone (DEXA, 1 mg/kg, orally) group, and two NAC groups (300 and 500 mg/kg, orally, respectively). Ovalbumin (OVA) sensitization was used to trigger asthma, which was then followed by an intra-nasal challenge. Test gents were administrated for 14 days before the challenge and during the three challenge days (20, 21, and 22). The tidal volume (TV) and peak expiratory flow rate (PEFR) as respiratory functions were determined. The pro-inflammatory cytokines as IL-5 and TNF-α were evaluated in lung homogenate. Serum IgE and absolute eosinophil count (AEC) in bronchoalveolar lavage fluid (BALF) were measured. In addition, the oxidative markers in lung tissue and nitrosative marker in BALF were assessed; finally, lungs were isolated for histopathological study.

Results

NAC restored lung functions, inhibited the asthma-dependent increase in TNF-α, IL-5, IgE, AEC, nitric oxide, and malondialdehyde levels. NAC further re-established lung glutathione content and superoxide dismutase activity, resulting in milder overall lung pathology.

Conclusions

Experimental bronchial asthma may be protected by NAC. The anti-asthmatic potential of NAC may be explained by its suppressant influence on IgE antibody formation, pro-inflammatory cytokines production, eosinophil infiltration, and oxidative stress.

Molecular mechanisms of oxidative stress in asthma

The lungs are exposed to reactive oxygen species oxygen (ROS) produced as a result of inhalation of oxygen, as well as smoke and other air pollutants. Cell metabolism and the NADPH oxidases (Nox) generate low levels of intracellular ROS that act as signal transduction mediators by inducing oxidative modifications of histones, enzymes and transcription factors. Redox signalling is also regulated by localised production and sensing of ROS in mitochondria, the endoplasmic reticulum (ER) and inside the nucleus. Intracellular ROS are maintained at low levels through the action of a battery of enzymatic and non-enzymatic antioxidants. Asthma is a heterogeneous airway inflammatory disease with different immune endotypes; these include atopic or non-atopic Th2 type immune response associated with eosinophilia, or a non-Th2 response associated with neutrophilia. Airway remodelling and hyperresponsiveness accompany the inflammatory response in asthma. Over-production of ROS resulting from infiltrating immune cells, particularly eosinophils and neutrophils, and a concomitant impairment of antioxidant responses lead to development of oxidative stress in asthma. Oxidative stress is augmented in severe asthma and during exacerbations, as well as by air pollution and obesity, and causes oxidative damage of tissues promoting airway inflammation and hyperresponsiveness. Furthermore, deregulated Nox activity, mitochondrial dysfunction, ER stress and/or oxidative DNA damage, resulting from exposure to irritants, inflammatory mediators or obesity, may lead to redox-dependent changes in cell signalling. ROS play a central role in airway epithelium-mediated sensing, development of innate and adaptive immune responses, and airway remodelling and hyperresponsiveness. Nonetheless, antioxidant compounds have proven clinically ineffective as therapeutic agents for asthma, partly due to issues with stability and in vivo metabolism of these compounds. The compartmentalised nature of ROS production and sensing, and the role of ROS in homeostatic responses and in the action of corticosteroids and β2-adrenergic receptor agonists, adds another layer of complexity to antioxidant therapy development. Nox inhibitors and mitochondrial-targeted antioxidants are in clinical development for a number of diseases but they have not yet been investigated in asthma. A better understanding of the complex role of ROS in the pathogenesis of asthma will highlight new opportunities for more targeted and effective redox therapies.

Review - Nutraceuticals Can Target Asthmatic Bronchoconstriction: NADPH Oxidase-Dependent Oxidative Stress, RhoA and Calcium Dynamics

Activation of various isoforms of NADPH oxidase contributes to the pathogenesis of asthma at multiple levels: promoting hypercontractility, hypertrophy, and proliferation of airway smooth muscle; enabling lung influx of eosinophils via VCAM-1; and mediating allergen-induced mast cell activation. Free bilirubin, which functions physiologically within cells as a feedback inhibitor of NADPH oxidase complexes, has been shown to have a favorable impact on each of these phases of asthma pathogenesis. The spirulina chromophore phycocyanobilin (PhyCB), a homolog of bilirubin’s precursor biliverdin, can mimic the inhibitory impact of biliverdin/bilirubin on NADPH oxidase activity, and spirulina’s versatile and profound anti-inflammatory activity in rodent studies suggests that PhyCB may have potential as a clinical inhibitor of NADPH oxidase. Hence, spirulina or PhyCB-enriched spirulina extracts merit clinical evaluation in asthma. Promoting biosynthesis of glutathione and increasing the expression and activity of various antioxidant enzymes – as by supplementing with N-acetylcysteine, Phase 2 inducers (eg, lipoic acid), selenium, and zinc – may also blunt the contribution of oxidative stress to asthma pathogenesis. Nitric oxide (NO) and hydrogen sulfide (H₂S) work in various ways to oppose pathogenic mechanisms in asthma; supplemental citrulline and high-dose folate may aid NO synthesis, high-dose biotin may mimic and possibly potentiate NO’s activating impact on soluble guanylate cyclase, and NAC and taurine may boost H₂S synthesis. The amino acid glycine has a hyperpolarizing effect on airway smooth muscle that is bronchodilatory. Insuring optimal intracellular levels of magnesium may modestly blunt the stimulatory impact of intracellular free calcium on bronchoconstriction. Nutraceutical regimens or functional foods incorporating at least several of these agents may have utility as nutraceutical adjuvants to standard clinical management of asthma.

Medical and Dietary Uses of N-Acetylcysteine

N-acetylcysteine (NAC), a plant antioxidant naturally found in onion, is a precursor to glutathione. It has been used as a drug since the 1960s and is listed on the World Health Organization (WHO) Model List of Essential Medicines as an antidote in poisonings. There are numerous other uses or proposed uses in medicine that are still in preclinical and clinical investigations. NAC is also used in food supplements and cosmetics. Despite its abundant use, there are projections that the NAC global market will grow in the next five years; therefore, the purpose of this work is to provide a balanced view of further uses of NAC as a dietary supplement. Although NAC is considered a safe substance, the results among clinical trials are sometimes controversial or incomplete, like for many other antioxidants. More clinical trials are underway that will improve our understanding of NAC applicability.

Exercise-Induced Bronchoconstriction and the Air We Breathe

An association between airway dysfunction and airborne pollutant inhalation exists. Volatilized airborne fluorocarbons in ski wax rooms, particulate matter, and trichloromines in indoor environments are suspect to high prevalence of exercise-induced bronchoconstriction and new-onset asthma in athletes competing in cross-country skiing, ice rink sports, and swimming. Ozone is implicated in acute decreases in lung function and the development of new-onset asthma from exposure during exercise. Mechanisms and genetic links are proposed for pollution-related new-onset asthma. Oxidative stress from airborne pollutant inhalation is a common thread to progression of airway damage. Key pollutants and mechanisms for each are discussed.

Oxidative stress in asthma: Part of the puzzle

An imbalance between the production of reactive oxygen species and the capacity of antioxidant defense mechanisms favoring oxidants is called oxidative stress and is implicated in asthmatic inflammation and severity. Major reactive oxygen species that are formed endogenously include hydrogen peroxide, superoxide anion, hydroxyl radical, and hypohalite radical; and the major antioxidants that fight against the endogenous and environmental oxidants are superoxide dismutase, catalase, and glutathione. Despite the well-known presence of oxidative stress in asthma, studies that target oxidative burden using a variety of nutritional, pharmacological, and environmental approaches have generally been disappointing. In this review, we summarize the current knowledge on oxidative stress and antioxidant imbalance in asthma. In addition, we focus on possible biomarkers of oxidative stress in asthma and on current and future treatment strategies using the modulation of oxidative stress to treat asthma patients.

A Review on Various Uses of N-Acetyl Cysteine

N-acetyl cysteine (NAC), as a nutritional supplement, is a greatly applied antioxidant in vivo and in vitro. NAC is a precursor of L-cysteine that results in glutathione elevation biosynthesis. It acts directly as a scavenger of free radicals, especially oxygen radicals. NAC is a powerful antioxidant. It is also recommended as a potential treatment option for different disorders resulted from generation of free oxygen radicals. Additionally, it is a protected and endured mucolytic drug that mellows tenacious mucous discharges. It has been used for treatment of various diseases in a direct action or in a combination with some other medications. This paper presents a review on various applications of NAC in treatment of several diseases.

Inhaled birch pollen extract induces airway hyperresponsiveness via oxidative stress but independently of pollen-intrinsic NADPH oxidase activity, or the TLR4-TRIF pathway

Oxidative stress in allergic asthma may result from oxidase activity or proinflammatory molecules in pollens. Signaling via TLR4 and its adaptor Toll-IL-1R domain-containing adapter inducing IFN-β (TRIF) has been implicated in reactive oxygen species-mediated acute lung injury and in Th2 immune responses. We investigated the contributions of oxidative stress and TLR4/TRIF signaling to experimental asthma induced by birch pollen exposure exclusively via the airways. Mice were exposed to native or heat-inactivated white birch pollen extract (BPEx) intratracheally and injected with the antioxidants, N-acetyl-L-cysteine or dimethylthiourea, prior to sensitization, challenge, or all allergen exposures, to assess the role of oxidative stress and pollen-intrinsic NADPH oxidase activity in allergic sensitization, inflammation, and airway hyperresponsiveness (AHR). Additionally, TLR4 signaling was antagonized concomitantly with allergen exposure, or the development of allergic airway disease was evaluated in TLR4 or TRIF knockout mice. N-acetyl-L-cysteine inhibited BPEx-induced eosinophilic airway inflammation and AHR except when given exclusively during sensitization, whereas dimethylthiourea was inhibitory even when administered with the sensitization alone. Heat inactivation of BPEx had no effect on the development of allergic airway disease. Oxidative stress-mediated AHR was also TLR4 and TRIF independent; however, TLR4 deficiency decreased, whereas TRIF deficiency increased BPEx-induced airway inflammation. In conclusion, oxidative stress plays a significant role in allergic sensitization to pollen via the airway mucosa, but the pollen-intrinsic NADPH oxidase activity and TLR4 or TRIF signaling are unnecessary for the induction of allergic airway disease and AHR. Pollen extract does, however, activate TLR4, thereby enhancing airway inflammation, which is restrained by the TRIF-dependent pathway.

N-acetylcysteine exerts therapeutic action in a rat model of allergic rhinitis

BACKGROUND

The pathophysiologic mechanism of allergy is dependent on the action of many redox-sensitive proinflammatory mediators. However, even though redox disturbances are believed to be a hallmark of inflammation, little is known of the effect of redox imbalance to the pathophysiology of allergic rhinitis. We thus opted to investigate the relation of oxidative stress and allergic rhinitis, through the utilization of a potent antioxidant substance (N-acetylcysteine [NAC]) in a rat model of allergic rhinitis and the evaluation of its action on specific markers of inflammation.

METHODS

NAC (50 mg/kg and 250 mg/kg) was intraperitoneally administered to ovalbumin (OVA)-sensitized rats prior to intranasal challenge with OVA. Mucosal congregation of inflammatory cells (eosinophils and mast cells), mucosal expression of redox-sensitive enzymes (inducible nitric oxide synthase [iNOS] and cyclooxygenase 2 [COX-2]), and the blood levels of a key proinflammatory mediator (tumor necrosis factor-α [TNF-α]) were evaluated.

RESULTS

Intranasal OVA challenges lead to mucosal inflammation, induction of the mucosal expression of iNOS and COX-2 and elevation of TNF-α blood levels. NAC significantly inhibited accumulation of inflammatory cells and downregulated iNOS expression and TNF-α serum levels. The role of COX-2 appeared to be 2-fold and its expression was divergently modulated by NAC.

CONCLUSION

Our findings suggest that redox balance is involved in the pathophysiology of allergic rhinitis in rats and that NAC can potentially suppress the allergen-induced nasal inflammatory cascade. The investigation of the role of oxidative stress in atopy could help in the evaluation of the therapeutic potential of antioxidant substances in allergic diseases.

Oxidative stress in asthma

Asthma is a chronic inflammatory lung disease that results in airflow limitation, hyperreactivity, and airway remodeling. There is strong evidence that an imbalance between the reducing and oxidizing systems favoring a more oxidative state is present in asthma. Endogenous and exogenous reactive oxygen species, such as superoxide anion, hydroxyl radical, hypohalite radical, and hydrogen peroxide, and reactive nitrogen species, such as nitric oxide, peroxynitrite, and nitrite, play a major role in the airway inflammation and are determinants of asthma severity. Asthma is also associated with decreased antioxidant defenses, such as superoxide dismutase, catalase, and glutathione. In this review, we will summarize the current knowledge and discuss the current and future strategies for the modulation of oxidative stress in asthma.

A novel dithiol amide CB3 attenuates allergic airway disease through negative regulation of p38 mitogen-activated protein kinase

RATIONALE

Cellular redox homeostasis altered by excessive production of reactive oxygen species (ROS) and weakening of the antioxidant defense leads to oxidative stress. Oxidative stress is characterized as a decrease in glutathione/glutathione disulfide (GSH/GSSG) and the triggering of a number of the redox-sensitive signaling cascades. Recent studies have demonstrated that ROS play an important role in the pathogenesis of airway inflammation and hyperresponsiveness.

OBJECTIVES

Here we characterized for the first time the protective properties of a new hydrophobic thiol compound, N-acetyl cysteine proline cysteine amide (CB3), in allergic airway diseases.

METHODS

We used ovalbumin (OVA)-inhaled mice to evaluate the role of CB3 as an antiinflammatory reagent and to determine its molecular signaling activity in allergic airways.

MEASUREMENTS AND MAIN RESULTS

The administration of CB3 (1-50 mg/kg) to OVA-inhaled mice restored the decreased GSH levels, enhanced IL-10 expression, and significantly reduced the increase of Th2 cytokines and OVA-specific IgE. CB3 decreased the number of inflammatory cells and airway hyperresponsiveness in the lungs. We also found that the administration of CB3 dramatically decreased the nuclear translocation of the nuclear factor-κB (NF-κB) and the phosphorylation of p38 mitogen-activated protein kinases (MAPKs) in lungs after OVA inhalation. In addition, allergen-induced airway inflammation and hyperresponsiveness were substantially reduced by the administration of inhibitors of NF-κB and p38 MAPK, BAY 11-7085, and SB 239063, respectively.

CONCLUSIONS

These results suggest that CB3 attenuates allergic airway disease by up-regulation of GSH levels as well as inhibition of NF-κB and p38 MAPK activity.

Oxidative stress and asthma: proteome analysis of chitinase-like proteins and FIZZ1 in lung tissue and bronchoalveolar lavage fluid

Oxidative stress plays an important role in the development of airway inflammation and hyperreactivity in asthma. The identification of oxidative stress markers in bronchoalveolar lavage fluid (BALF) and lung tissue from ovalbumin (OVA) sensitized mice could provide new insight into disease pathogenesis and possible use of antioxidants to alleviate disease severity. We used two-dimensional polyacrylamide gel electrophoresis (2D-PAGE) and liquid chromatography-tandem mass spectrometry (LC-MS/MS) to determine the impact of the thiol antioxidant, N-acetylcysteine (NAC), on protein expression in a murine OVA model. At least six proteins or protein families were found to be significantly increased in BALF from OVA-challenged mice compared to a control group: Chitinase 3-like protein 3 (Yml), Chitinase 3-like protein 4 (Ym2), acidic mammalian Chitinase (AMCase), pulmonary surfactant-associated protein D (SP-D), resistin-like molecule alpha (RELMalpha) or "found in inflammatory 1" (FIZZ1), and haptoglobin alpha-subunit. A total of nine proteins were significantly increased in lung tissue from the murine asthma model, including Yml, Ym2, FIZZ1, and other lung remodeling-related proteins. Western blotting confirmed increased Yml/Ym2, SP-D, and FIZZ1 expression measured from BAL fluid and lung tissue from OVA-challenged mice. Intraperitoneal NAC administration prior to the final OVA challenge inhibited Yml/Ym2, SP-D, and FIZZ1 expression in BALF and lung tissue. The oxidative stress proteins, Ym1/Ym2, FIZZ1, and SP-D, could play an important role in the pathogenesis of asthma and may be useful oxidative stress markers.

Effects of oral alpha-tocopherol on lung response in rat model of allergic asthma

OBJECTIVE AND BACKGROUND

Asthma is a chronic inflammatory disease in which an oxidant/antioxidant imbalance plays an important role. d-alpha-tocopherol (biologically the most active form of vitamin E) has redox properties and by scavenging the free radicals can act as an antioxidant. The aim of this study was to examine the effects of orally administered alpha-tocopherol in a rat model of allergic asthma.

METHODOLOGY

Actively sensitized rats (OA) were treated with alpha-tocopherol (400 mg/kg/day for 10 days) or vehicle; 1 h after the last dose, they were challenged with antigen aerosol. The antigen-induced airway hyperresponsiveness to direct bronchoconstrictor (serotonin), the inflammatory cell infiltrate and histological changes were determined 1 or 24 h after the antigen challenge.

RESULTS

Alpha-tocopherol pretreatment was not significantly effective at reducing the studied parameters when compared with controls, even though there was a tendency to a reduction in bronchial responsiveness and in eosinophil and neutrophil infiltration.

CONCLUSION

Alpha-tocopherol when administered in the chosen study design in an animal model of asthma had no major effect on airway inflammation. The effect of antioxidants deserves further evaluation.

Protective role of l-2-oxothiazolidine-4-carboxylic acid in cisplatin-induced renal injury

BACKGROUND

Oxidative stress and inflammation are implicated in the pathogenesis of cisplatin-induced nephrotoxicity. l-2-oxothiazolidine-4-carboxylic acid (OTC) is a cysteine prodrug, and increases cellular glutathione (GSH). OTC is converted to cysteine by the intracellular enzyme, oxoprolinase. To date, the protective role of OTC on cisplatin-induced renal injury has not been investigated. The purpose of the present study was to examine the protective effect of OTC on cisplatin-induced renal injury and to examine the mechanism of its protection.

METHODS

Mice were treated with cisplatin with or without administration of OTC. The generation of reactive oxygen species (ROS), expression of intercellular adhesion molecule (ICAM)-1 and monocyte chemoattractant protein (MCP)-1 were determined in the kidney using 2',7'-dichlorofluorescein diacetate, immunostaining or western blot analysis. Nuclear factor (NF)-kappaB activity, infiltration of F4/80-positive cells and apoptosis were also investigated in addition to renal function and histology using electrophoretic mobility shift assay, immunostaining, western blot analysis, uridine triphosphate (dUTP) nick-end labelling or periodic acid-Schiff staining. The effect of OTC on superoxide dismutase activity and GSH level in cisplatin-treated normal adult human kidney (HK-2) cells were measured using assay kits.

RESULTS

The administration of OTC resulted in a significant reduction of cisplatin-induced ROS production, the p65 subunit of NF-kappaB translocation into nucleus, expression of ICAM-1, caspase 3 activity, expression of MCP-1 and the infiltration of macrophages into renal tissue. OTC markedly ameliorated renal damage induced by cisplatin through antioxidant and anti-inflammatory effect.

CONCLUSIONS

These results suggest that OTC can be a potential therapeutic agent in cisplatin-induced renal injury through decreasing the ROS levels and activation of NF-kappaB.

A prodrug of cysteine, L-2-oxothiazolidine-4-carboxylic acid, regulates vascular permeability by reducing vascular endothelial growth factor expression in asthma

Inflammation of the asthmatic airway is usually accompanied by increased vascular permeability and plasma exudation. Oxidative stress plays critical roles in airway inflammation. Although reactive oxygen species (ROS) are shown to cause vascular leakage, the mechanisms by which ROS induce increased vascular permeability are not clearly understood. We have used a murine model of asthma to evaluate the effect of l-2-oxothiazolidine-4-carboxylic acid (OTC), a prodrug of cysteine that acts as an antioxidant, more specifically in the increase of vascular permeability. These mice develop the following typical pathophysiological features of asthma in the lungs: increased numbers of inflammatory cells of the airways, airway hyper-responsiveness, increased vascular permeability, and increased levels of vascular endothelial growth factor (VEGF). Administration of OTC markedly reduced plasma extravasation and VEGF levels in allergen-induced asthmatic lungs. We also showed that at 72 h after ovalbumin inhalation, increased levels of hypoxia-inducible factor-1alpha (a transcriptional activator of VEGF) in nuclear protein extracts of lung tissues were decreased by the administration of OTC. These results indicate that OTC modulates vascular permeability by lowering VEGF expression.

The effect of N-acetylcysteine on Clara cells and Clara cell 16 kDa protein in a murine model of allergen-induced airway inflammation

OBJECTIVE

The aim of this study was to investigate the number of Clara cells and the production and secretion of Clara cell 16 kDa protein (CC16) in a murine model of allergen-induced airway inflammation, as well as the effects of N-acetylcysteine (NAC) on CC16 and Clara cell numbers, in order to determine the mechanism of the anti-inflammatory effect of NAC.

METHODOLOGY

BALB/c mice were divided into control, ovalbumin (OVA) and NAC groups. An allergen-induced airway inflammation model (OVA group) was established by sensitizing and challenging mice with OVA. NAC was administered as an oral treatment. The number of Clara cells and the production of CC16 were determined by immunohistochemistry. The CC16 levels in bronchoalveolar lavage fluid (BALF) were determined by Western blotting.

RESULTS

The proportion of Clara cells in terminal and respiratory bronchioles significantly decreased in the OVA group compared to the control group (P < 0.01). NAC treatment did not change the proportion of Clara cells in the OVA group (P > 0.05). CC16 production by Clara cells in the OVA groups was significantly lower than that of the control group (P < 0.01), but was elevated following NAC treatment (P < 0.05). The CC16 level in BALF of the OVA group was lower than that of the control group (P < 0.01), but was elevated by NAC treatment (P < 0.05). NAC reduced the total number of white cells and the percentage of eosinophils in BALF. Moreover, it inhibited airway inflammation.

CONCLUSIONS

The number of Clara cells and the production and secretion of CC16 were reduced in a murine model of allergen-induced airway inflammation. Antioxidants can enhance the expression of CC16, which might be a mechanism by which they suppress airway inflammation.

Blockade of airway hyperresponsiveness and inflammation in a murine model of asthma by a prodrug of cysteine, L-2-oxothiazolidine-4-carboxylic acid

Oxidative stress plays an important role in the pathogenesis of bronchial asthma. An excess production of reactive oxygen species (ROS) and defective endogenous antioxidant defense mechanisms may be present in asthma. Reduced glutathione (GSH) is one of the most important reducing agents against oxidant free radicals. A reducing agent, L-2-oxothiazolidine-4-carboxylic acid (OTC), a prodrug of cysteine, increases intracellular GSH. We have used a mouse model for asthma to determine effects of OTC on allergen-induced bronchial inflammation and airway hyper-responsiveness. The administration of OTC reduced bronchial inflammation and airway hyper-responsiveness. ROS generation in bronchoalveolar lavage fluids was increased by ovalbumin (OVA) inhalation, but this increase was diminished by administration of OTC. The increased IL-4, IL-5, IL-13, and eosinophil cationic protein levels in lungs after OVA inhalation were significantly reduced by the administration of OTC. In addition, the increased expression of ICAM-1, VCAM-1, RANTES, and eotaxin in lungs after OVA inhalation was significantly reduced by the administration of OTC. We also showed that the increased NF-kappaB levels in nuclear protein extracts of lung tissues at 72 h after OVA inhalation were decreased by the administration of OTC. These findings suggest that OTC may reduce airway inflammation and hyper-responsiveness through regulation of NF-kappaB activity.

alpha-Lipoic acid inhibits airway inflammation and hyperresponsiveness in a mouse model of asthma

BACKGROUND

Oxidative stress may play an important role in the pathogenesis of bronchial asthma.

OBJECTIVE

We evaluated the therapeutic effect of alpha-lipoic acid, a nonenzymatic antioxidant, in a mouse model of asthma.

METHODS

BALB/c mice were immunized intraperitoneally with ovalbumin (OVA) on days 1 and 14 and challenged with inhaled OVA on days 28, 29, and 30. Mice were fed OVA-free standard mouse chow with 0%, 0.125%, 0.25%, 0.5%, and 1% (wt/wt) alpha-lipoic acid during the immunization and challenge periods. On day 31, mice were challenged with inhaled methacholine, and enhanced pause was measured as an index of airway hyperresponsiveness. Severity of airway inflammation was determined by means of differential cell count of bronchoalveolar lavage (BAL) fluid and by means of histopathologic lung analysis. Levels of OVA-specific IgE in serum, IL-4 and IL-5 in BAL fluid, and intracellular reactive oxygen species in alveolar macrophages and lymphocytes obtained from regional perihilar lymph nodes were measured. Nuclear factor kappaB DNA-binding activity in lung tissues was analyzed by means of electrophoretic gel mobility shift assay.

RESULTS

Compared with untreated asthmatic mice, mice treated with alpha-lipoic acid had significantly reduced airway hyperresponsiveness, a lower proportion of eosinophils among BAL cells, and significantly improved pathologic lesion scores of the lungs. alpha-Lipoic acid also significantly reduced serum OVA-specific IgE concentrations, IL-4 and IL-5 concentrations in BAL fluid, and intracellular reactive oxygen species and nuclear factor kappaB DNA-binding activity.

CONCLUSION

These results suggest that oxidative stress plays an important role in asthmatic airway inflammation and that alpha-lipoic acid may be useful as adjuvant therapy for bronchial asthma.

The role of oxidative stress in chronic obstructive pulmonary disease

Tobacco smoke is the number one risk factor for chronic obstructive pulmonary disease (COPD) and contains a high concentration of oxidants. The lung has a high concentration of antioxidants and antioxidant enzymes; however, COPD patients show evidence of increased oxidative stress suggesting that endogenous antioxidants may be insufficient to prevent oxidative damage from cigarette smoke. The consequences of increased oxidative stress in the lung include increased transcription of inflammatory genes, increased protease activity, and increased mucus secretion. Oxidative stress is often associated with impaired skeletal muscle function and may be one of the causes of glucocorticoid resistance. While current pharmacologic approaches to the treatment of chronic obstructive pulmonary disease do not commonly include antioxidants, preclinical studies involving animal models suggest that antioxidant superoxide dismutase mimetics offer a potential new therapeutic approach to the prevention and treatment of chronic obstructive pulmonary disease.