Is oxidative stress associated with disease severity, pulmonary function and metabolic syndrome in chronic obstructive pulmonary disease?

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.

Pulmonary function is associated with frailty, hospitalization and mortality in older people: 5-year follow-up

BACKGROUND

The relationship between pulmonary impairment and frailty has rarely been studied in community-dwelling older adults.

OBJECTIVE

This study aimed to analyze the association between pulmonary function and frailty (prevalent and incident), identifying the best cut-off points to detect frailty and its association with hospitalization and mortality.

METHODS

A longitudinal observational cohort study with 1188 community-dwelling older adults was taken from the Toledo Study for Healthy Aging. The forced expiratory volume in the first second (FEV₁) and the forced vital capacity (FVC) were measured with spirometry. Frailty was evaluated using the Frailty Phenotype and Frailty Trait Scale 5. Associations between pulmonary function and frailty, hospitalization and mortality in a 5-year follow-up and the best cut-off points for FEV₁ and FVC were analyzed.

RESULTS

FEV₁ and FVC were associated with frailty prevalence (OR from 0.25 to 0.60), incidence (OR from 0.26 to 0.53), and hospitalization and mortality (HR from 0.35 to 0.85). The cut-off points of pulmonary function identified in this study: FEV1 (≤1.805 L for male and ≤1.165 L for female) and FVC (≤2.385 L for male and ≤1.585 L for female) were associated with incident frailty (OR: 1.71-4.06), hospitalization (HR: 1.03-1.57) and mortality (HR: 2.64-5.17) in individuals with and without respiratory diseases (P < 0.05 for all).

CONCLUSION

Pulmonary function was inversely associated with the risk of frailty, hospitalization and mortality in community-dwelling older adults. The cut-off points for FEV₁ and FVC to detect frailty were highly associated with hospitalization and mortality in the 5-year follow-up, regardless of the existence of pulmonary diseases.

Paraoxonase 1 and Chronic Obstructive Pulmonary Disease: A Meta-Analysis

Oxidative stress is a driving factor in the pathophysiology of chronic obstructive pulmonary disease (COPD). While paraoxonase 1 (PON1) is an antioxidant enzyme and a potential biomarker of this disease, data regarding the status of PON-1 in COPD are inconclusive. In this regard, to shed light on this issue, we performed a meta-analysis of data on PON1 activity in COPD. Electronic databases (MEDLINE, Embase and CENTRAL) were searched for available studies on PON1 activity in patients with stable COPD published before October 2021. A meta-analysis was performed using random-effects models. Twelve studies (12 studies on paraoxonase and three on arylesterase) were identified. Patients with COPD had lower levels of paraoxonase activity (standard mean difference [SMD] -0.77, 95% confidence interval [CI] -1.35 to -0.18) and arylesterase activity (SMD -1.15, 95% CI -1.95 to -0.36) in comparison to healthy controls. In subgroup analyses, paraoxonase activity was lower in patients of studies as consisted of mainly non-severe COPD (SMD -1.42, 95% CI -2.04 to -0.79) and, by contrast, slightly higher in patients of studies including severe COPD (SMD 0.33, 95% CI 0.02 to 0.64) in comparison to healthy controls. Arylesterase activity showed a similar trend. Overall, PON1 activity was lower in patients with COPD, suggesting that PON1-related antioxidant defense is impaired in COPD. Future studies are warranted.

Are oxidative stress biomarkers and respiratory muscles strength associated with COPD-related sarcopenia in older adults?

BACKGROUND

Patients with chronic obstructive pulmonary disease (COPD) often present with sarcopenia, a condition marked by the loss in quality and quantity of muscle mass that can affect the strength of respiratory muscles. COPD and sarcopenia are also independently associated with oxidative stress. This study aimed to investigate whether oxidative stress biomarkers and respiratory muscle strength are associated with sarcopenia in COPD patients.

METHODS

In a cross-sectional study, 86 elderly subjects, including subjects with and without COPD were assessed for body composition, maximal inspiratory pressure (MIP) and maximal expiratory pressure (MEP) and oxidative stress parameters [substances reactive to thiobarbituric acid (TBARS), ferric reducing ability of plasma (FRAP), superoxide dismutase (SOD), and catalase (CAT)].

RESULTS

The sample was mainly composed by males (72.1%) and eutrophic subjects. COPD-related sarcopenia was evidenced in 51.1% (22/43) of subjects with COPD. The highest TBARS and CAT, and lower MIP and MEP were associated with a high probability of having COPD-related sarcopenia. In the multivariate analysis, TBARS (OR: 4.89, 95% CI 1.52 to 15.54, p = 0.006), CAT (OR: 1.22, 95% CI 1.03 to 1.45, p = 0.020) and MEP (OR: 0.97, 95% CI 0.95 to 0.99, p = 0.020) were independent determinants of COPD-related sarcopenia.

CONCLUSION

The increase in oxidative stress-related factors and the reduction of respiratory muscle strength are associated with COPD-related sarcopenia.