Antioxidant therapeutic advances in COPD

Chronic obstructive pulmonary disease (COPD) is associated with a high incidence of morbidity and mortality. Cigarette smoke-induced oxidative stress is intimately associated with the progression and exacerbation of COPD and therefore targeting oxidative stress with antioxidants or boosting the endogenous levels of antioxidants is likely to have beneficial outcome in the treatment of COPD. Among the various antioxidants tried so far, thiol antioxidants and mucolytic agents, such as glutathione, N-acetyl-L-cysteine, N-acystelyn, erdosteine, fudosteine and carbocysteine; Nrf2 activators; and dietary polyphenols (curcumin, resveratrol, and green tea catechins/quercetin) have been reported to increase intracellular thiol status along with induction of GSH biosynthesis. Such an elevation in the thiol status in turn leads to detoxification of free radicals and oxidants as well as inhibition of ongoing inflammatory responses. In addition, specific spin traps, such as α-phenyl-N-tert-butyl nitrone, a catalytic antioxidant (ECSOD mimetic), porphyrins (AEOL 10150 and AEOL 10113), and a SOD mimetic M40419 have also been reported to inhibit cigarette smoke-induced inflammatory responses in vivo in the lung. Since a variety of oxidants, free radicals and aldehydes are implicated in the pathogenesis of COPD, it is possible that therapeutic administration of multiple antioxidants and mucolytics will be effective in management of COPD. However, a successful outcome will critically depend upon the choice of antioxidant therapy for a particular clinical phenotype of COPD, whose pathophysiology should be first properly understood. This article will review the various approaches adopted to enhance lung antioxidant levels, antioxidant therapeutic advances and recent past clinical trials of antioxidant compounds in COPD

Nacystelyn, a novel lysine salt of N-acetylcysteine, to augment cellular antioxidant defence in vitro

AbstractNacystelyn (NAL), a recently-developed lysine salt of N-acetylcysteine (NAC), and NAG, both known to have excellent mucolytic capabilities, were tested for their ability to enhance cellular antioxidant defence mechanisms. To accomplish this, both drugs were tested in vitro for their capacity: (1) to inhibit O2− and H2O2 in cell-free assay systems; (2) to reduce O2− and H2O2 released by polymorphonuclear leukocytes (PMN); and (3) for their cellular glutathione (GSH) precursor effect.In comparison with GSH, NAL and NAC inhibited H2O2, but not O2−, in cell-free, in vitro test systems in a similar manner. The anti-H2O2 effect of these drugs was as potent as that of GSH, an important antioxidant in mammalian cells. To enhance cellular GSH levels, increasing concentrations (0–2 × 10−4 mol 1−1) of both substances were added to a transformed alveolar cell line (A549 cells). After NAC administration (2 × 10−4 mol 1−1), total intracellular GSH (GSH + 2GSSG) levels reached 4·5 ± 1·1 × 10−6 mol per 106 cells, whereas NAL increased GSH to 8·3 ± 1·6 × 10−6 mol per 106 cells. NAC and NAL administration also induced extracellular GSH secretion; about two-fold (NAC), and 1·5-fold (NAL), respectively. The GSH precursor potency of cystine was about two-fold higher than that of NAL and NAC, indicating that the deacetylation process of NAL and NAC slows the ability of both drugs to induce cellular glut production and secretion. Buthionine-sulphoximine, which is an inhibitor of GSH synthetase, blocked the cellular GSH precursor effect of all substances. In addition, these data demonstrate that NAC and NAL reduce H2O2 released by freshly-isolated cultured blood PMN from smokers with chronic obstructive pulmonary disease (COPD) (n=10) in a similar manner (about 45% reduction of H2O2 activity by NAC or NAL at 4 × 10−6 mol 1−1). In accordance with the results obtained from cell-free, in vitro assays, O2− released by PMN was not affected. Ambroxol (concentrations: 10−9−10−3 mol 1−1) did not reduce activity levels of H2O2 and O2− in vitro. Due to the basic effect of dissolved lysine, which separates easily in solution from NAL, the acidic function of the remaining NAC molecule is almost completely neutralized [at concentration 2 × 10−4 M: pH 3·6 (NAC), pH 6·4 (NAL)].Due to their function as H2O2 scavengers, and due to their ability to enhance cellular glutathione levels, NAL and NAC both have potent antioxidant capabilities in vitro. The advantage of NAL over NAC is two-fold; it enhances intracellular GSH levels twice as effectively, and it forms neutral pH solutions whereas NAC is acidic. Concluding from these in vitro results, NAL could be an interesting alternative to enhance the antioxidant capacity at the epithelial surface of the lung by aerosol administration

A single bout of resistance exercise triggers mitophagy, potentially involving the ejection of mitochondria in human skeletal muscle.

The present study aimed to investigate the effects of a single bout of resistance exercise on mitophagy in human skeletal muscle (SkM). Eight healthy men were recruited to complete an acute bout of one-leg resistance exercise. SkM biopsies were obtained one hour after exercise in the resting leg (Rest-leg) and the contracting leg (Ex-leg). Mitophagy was assessed using protein-related abundance, transmission electron microscopy (TEM), and fluorescence microscopy. Our results show that acute resistance exercise increased pro-fission protein phosphorylation (DRP1 <sup>Ser616</sup> ) and decreased mitophagy markers such as PARKIN and BNIP3L/NIX protein abundance in the Ex-leg. Additionally, mitochondrial complex IV decreased in the Ex-leg when compared to the Rest-leg. In the Ex-leg, TEM and immunofluorescence images showed mitochondrial cristae abnormalities, a mitochondrial fission phenotype, and increased mitophagosome-like structures in both subsarcolemmal and intermyofibrillar mitochondria. We also observed increased mitophagosome-like structures on the subsarcolemmal cleft and mitochondria in the extracellular space of SkM in the Ex-leg. We stimulated human primary myotubes with CCCP, which mimics mitophagy induction in the Ex-leg, and found that BNIP3L/NIX protein abundance decreased independently of lysosomal degradation. Finally, in another human cohort, we found a negative association between BNIP3L/NIX protein abundance with both mitophagosome-like structures and mitochondrial cristae density in the SkM. The findings suggest that a single bout of resistance exercise can initiate mitophagy, potentially involving mitochondrial ejection, in human skeletal muscle. BNIP3L/NIX is proposed as a sensitive marker for assessing mitophagy flux in SkM