Use of thiols and implications for the use of inhaled corticosteroids in the presence of oxidative stress in COPD

BACKGROUND

Oxidative stress and persistent airway inflammation are thought to be important contributors to the development of chronic obstructive pulmonary disease (COPD). This review summarizes the evidence for targeting oxidative stress and inflammation in patients with COPD with mucolytic/antioxidant thiols and inhaled corticosteroids (ICS), either alone or in combination.

MAIN BODY

Oxidative stress is increased in COPD, particularly during acute exacerbations. It can be triggered by oxidant air pollutants and cigarette smoke and/or by endogenous reactive oxygen species (ROS) released from mitochondria and activated inflammatory, immune and epithelial cells in the airways, together with a reduction in endogenous antioxidants such as glutathione (GSH). Oxidative stress also drives chronic inflammation and disease progression in the airways by activating intracellular signalling pathways and the release of further inflammatory mediators. ICS are anti-inflammatory agents currently recommended for use with long-acting bronchodilators to prevent exacerbations in patients with moderate-to-severe COPD, especially those with eosinophilic airway inflammation. However, corticosteroids can also increase oxidative stress, which may in turn reduce corticosteroid sensitivity in patients by several mechanisms. Thiol-based agents such as erdosteine, N-acetyl L-cysteine (NAC) and S-carboxymethylcysteine (S-CMC) are mucolytic agents that also act as antioxidants. These agents may reduce oxidative stress directly through the free sulfhydryl groups, serving as a source of reducing equivalents and indirectly though intracellular GSH replenishment. Few studies have compared the effects of corticosteroids and thiol agents on oxidative stress, but there is some evidence for greater antioxidant effects when they are administered together. The current Global Initiative for Chronic Obstructive Lung Disease (GOLD) report supports treatment with antioxidants (erdosteine, NAC, S-CMC) in addition to standard-of-care therapy as they have been demonstrated to reduce COPD exacerbations. However, such studies have demonstrated that NAC and S-CMC reduced the exacerbation risk only in patients not treated with ICS, whereas erdosteine reduced COPD exacerbations irrespective of concomitant ICS use suggesting that erdosteine has additional pharmacological actions to ICS.

CONCLUSIONS

Further clinical trials of antioxidant agents with and without ICS are needed to better understand the place of thiol-based drugs in the treatment of patients with COPD.

Multifaceted Beneficial Effects of Erdosteine: More than a Mucolytic Agent

Erdosteine is a drug approved for the treatment of acute and chronic pulmonary diseases, originally developed as a mucolytic agent. It belongs to the thiol-based family of drugs that are known to also possess potentially important antioxidant and anti-inflammatory properties, and exhibit antibacterial activity against a variety of medically important bacterial species. Erdosteine is a prodrug that is metabolized to the ring-opening compound metabolite M1 (MET 1), which has mucolytic properties. Experimental studies have documented that erdosteine prevents or reduces lung tissue damage induced by oxidative stress and, in particular, that Met 1 also regulates reactive oxygen species production. The RESTORE study, which has been the only trial that investigated the effects of a thiol-based drug in chronic obstructive pulmonary disease (COPD) frequent exacerbators, documented that erdosteine significantly reduces the risk of acute exacerbations of COPD (AECOPDs), shortens their course, and also decreases the risk of hospitalization from COPD. The preventive action of erdosteine on AECOPDs was not affected by the presence or absence of inhaled corticosteroids (ICSs) or blood eosinophil count. These findings clearly contrast with the Global Initiative for Chronic Obstructive Lung Disease strategy’s approach to use erdosteine only in those COPD patients not treated simultaneously with an ICS. Furthermore, they support the possibility of using erdosteine in a step-down approach that in COPD is characterized by the withdrawal of the ICS.

The effect of erdosteine on airway defence mechanisms and inflammatory cytokines in the settings of allergic inflammation

INTRODUCTION

Mucoactive agent, erdosteine, besides mucolytic activity, is characterized by many other pharmacodynamic properties which could be beneficial in the management of inflammatory conditions.

BACKGROUND

Using guinea pig experimental model of allergic inflammation, we evaluated the ability of erdosteine to modulate airway defence mechanisms and inflammation after 10 days (10 mg/kg/day) administration.

METHODS

In vivo changes in specific airway resistance and amplitude of tracheal contraction were estimated to evaluate the bronchodilatory effect. The sensitivity of chemically induced cough reflex was estimated via in vivo method. The ciliary beat frequency assessed on brushed tracheal cells was used as an indicator of the mucociliary clearance rate. The concentrations of the inflammatory cytokines IL-4, IL-5, IL-13 and IL-10 were measured in BALF using multiplex detecting method.

RESULTS

Our data show that 10 days erdosteine administration resulted in bronchodilation and stimulation of ciliary beat frequency. Erdosteine did not affect the parameters of chemically induced cough reflex. Erdosteine demonstrated the modest decline in inflammatory cytokines IL-5, IL-13 and an increase in the concentration of IL-10, which is a potent regulator of inflammatory responses and plays a critical role in controlling allergic airway inflammation.

CONCLUSION

In summary, we can state, that erdosteine is multi-action drug and it seems to have many beneficial and complementary effect in the management of chronic inflammatory airway diseases complicated by viscous mucus.

Effects of Erdosteine in Experimental Sepsis Model in Rats

Objective

Erdosteine is a mucolytic agent that is known to possess antioxidant effects. This study investigated the effects of erdosteine on endothelin-1 (ET-1) levels and oxidative stress parameters superoxide dismutase (SOD) and malondialdehyde (MDA) in a rat sepsis model.

Methods

Four groups of Wistar albino rats (n=8 per group) were randomly allocated to the following groups: sham (group 1), sepsis (group 2), erdosteine control (group 3) and a sepsis group pretreated with erdosteine (group 4). Sepsis was induced using E. Coli ATCC 25922 inoculation. Serum ET-1, liver tissue SOD and MDA levels were determined in all groups.

Results

ET-1 levels were significantly higher in group 2 compared to groups 1, 3 and 4 (p<0.001, p=0.002 and p<0.001, respectively). Similarly, MDA levels in groups 1, 3 and 4 were significantly lower relative to group 2 (p<0.001, p=0.022 and p=0.010, respectively). Additionally, SOD activities in these same three groups were found to be significantly higher than those in group 2 (p<0.001, p=0.004 and p=0.028, respectively).

Conclusion

In conclusion, erdosteine decreases ET-1 levels and ameliorates oxidative stress parameters induced by sepsis in an experimental rat model of sepsis.

Acute and Chronic Effects of Oral Erdosteine on Ciliary Beat Frequency, Cough Sensitivity and Airway Reactivity

Erdosteine as a mucolytic agent that decreases mucus viscosity and facilitates mucus expulsion from the airways by cough or ciliary movement. Our objective was to determine whether erdosteine can directly contribute to mucus clearance. We addressed the issue by monitoring acute and chronic effects of erdosteine on ciliary beat frequency (CBF), cough sensitivity, and airway smooth muscle reactivity. The experiments were performed in healthy guinea pigs. Erdosteine (10 mg/kg) was administrated orally in a single dose or daily through 7 days. The cough reflex and specific airway resistance were evaluated in vivo. The CBF in tracheal brushed samples and the contractile response of tracheal smooth muscle stripes to bronchoconstrictive mediators were evaluated in vitro. We found that neither acute nor chronic erdosteine treatment had a significant effect on cough sensitivity and airway reactivity. However, in the vitro condition, erdosteine increased CBF and reduced tracheal smooth muscle contractility; the effects were more pronounced after chronic treatment. We conclude that erdosteine may directly contribute to mucus clearance by CBF stimulation. Although erdosteine has no effect on cough reflex sensitivity, its mild bronchodilator and mucolytic properties may promote effective cough.

Priming of beta-2 agonist and antimuscarinic induced physiological responses induced by 1200mg/day NAC in moderate to severe COPD patients: A pilot study

This study evaluated antioxidant modulations of lung physiological-responses to beta-2-agonist and antimuscarinic bronchodilators with 1200mg/day n-acetyl-cysteine (NAC) in a placebo-controlled, randomised, double-blind, parallel-group study, in moderate-very severe COPD patients.

METHODS

15 COPD patients received NAC treatment, while 9 COPD patients received placebo treatment, for 15 days. Pre-and-post salbutamol and ipratopium-bromide lung-physiology responses were measured using body-plethysmography, impulse-oscillometry (IOS) and spirometry before-and-after study treatments.

RESULTS

Compared to pre-treatment, the NAC-treatment significantly enhanced the potential of ipratopium-bromide to reduce functional-residual-capacity (FRC) by nearly 3-folds (mean% FRC-response: pre-NAC: -5.51%±10.42% versus post-NAC: -17.89%±12.94%, p=0.02; mean-absolute FRC-response: pre-NAC: -300ml±450ml versus post-NAC: -770ml±550ml, p=0.02), which was superior to placebo-treatment. The increase in total-lung-capacity response to ipratopium-bromide, although insignificant, was superior with post-NAC treatment versus post-placebo treatment (p=0.049). The salbutamol-response remained unaltered with either treatment.

CONCLUSION

The treatment with 1200mg/day NAC has potential to enhance the bronchodilator ability of antimuscarinic-agents but not beta-2-agonist. However, its clinical application has to be established in large sample-size studies for longer-duration.

Rationale for earlier treatment in COPD: a systematic review of published literature in mild-to-moderate COPD

COPD is progressive and typically begins many years before a definite diagnosis is made. As the rate of decline in lung function may be faster in the initial stages of the disease, early intervention could be beneficial to control symptoms and affect disease progression and outcomes. A systematic review of published literature relating to mild-to-moderate COPD (patients with FEV(1) ≥50% predicted) was performed to evaluate the level of impairment and natural history or disease progression over time, and impact of interventions on the outcomes of patients with early-stage disease. Of the 79 published articles included in this analysis, 31 reported randomized controlled trials; the remaining 48 articles reported studies of non-randomized and/or observational design. Nine of the randomized controlled trials were ≥6 months' duration, enabling assessment of outcomes over time. Most of the randomized controlled trials were in patients with moderate COPD (GOLD stage II); few included patients with the mildest stages of the disease (i.e., stage I). The results show that even patients with milder or moderate COPD can have substantial limitations and physical impairment, which worsen over time. Encouragement of smoking cessation, in conjunction with management of symptoms and treating activity limitation and exacerbations by appropriate non-pharmacologic and pharmacologic management at the earliest possible stage, could positively affect the impact and progression of the disease.

Erdosteine: its relevance in COPD treatment

BACKGROUND

Chronic obstructive pulmonary disease (COPD) is a progressive condition characterized by airflow limitation, which is largely irreversible; the oxidant/antioxidant imbalance is important in the pathogenesis of this condition.

OBJECTIVE

To show that administration of erdosteine, a mucolytic agent with a prevalent antioxidant activity, could play a beneficial role in COPD.

METHODS

To review the experimental and clinical trials on erdosteine in COPD and chronic bronchitis.

RESULTS

Erdosteine is a thiol agent with a multifactorial mechanism of action, namely: mucolytic, antibacterial, antioxidant and anti-inflammatory activity. In the acute exacerbation of chronic bronchitis/COPD, addition of erdosteine 300 mg twice a day for 7 - 10 days to standard treatment improves the symptoms and reduces the time of disease. In clinically stable COPD, long-term treatment is associated with a reduction in acute exacerbation and hospitalization rate and a significant improvement of quality of life. Erdosteine could be most beneficial in patients who have repeated, prolonged or severe exacerbations of COPD.