Pharmacological investigation on the anti-oxidant and anti-inflammatory activity of N-acetylcysteine in an ex vivo model of COPD exacerbation

Abstract

BackgroundOxidative stress is recognized to be one of predisposing factor in the pathogenesis of COPD. The oxidant/antioxidant imbalance is significantly pronounced in patients with COPD exacerbation. N-acetylcysteine (NAC) seems to be able to reduce COPD exacerbations by modulating the oxidative stress in addition to its well-known mucolytic activity, but there are discordant findings on the actual anti-oxidant activity of NAC.MethodsThe anti-oxidant effect of NAC and its impact on the inflammatory response have been pharmacologically characterized on a human ex vivo model of COPD exacerbation induced by lipopolysaccharide (LPS).ResultsNAC prevented the desensitization induced by LPS incubation on the contractile tone in linear concentration-response manner. Concentrations of NAC ≥1 μM reduced the pro-oxidant response (peroxidase activity, hydrogen peroxide, malondialdehyde, nitric oxide), and improved the anti-oxidant response (total anti-oxidant capacity, glutathione, superoxide dismutase) induced by LPS. Lower concentrations of NAC (<1 μM) did not modulate the bronchial oxidative imbalance. Concentrations of NAC ≥300 μM inhibited the inflammatory response (release of IL-1β, IL-8, and TNF-α) of human airways induced by the overnight stimulation with LPS, whereas lower concentrations of NAC (≥1 μM) were sufficient to reduce the release of IL-6 elicited by LPS. Both the anti-oxidant effect and the anti-inflammatory effect of NAC were inversely correlated with the release of NKA.ConclusionsThe findings of this study suggest that NAC may have a role in modulating the detrimental effect induced by LPS in course of COPD exacerbation. It may elicit both anti-oxidant and anti-inflammatory effects when administered at high concentrations.

Effect of lipopolysaccharide on the responsiveness of equine bronchial tissue

“…Conversely, the overnight challenge with LPS at higher concentrations (100 ng/ml) inhibited the bronchial contractility in response to medium-high EFS frequencies. The bronchial desensitization of equine airways induced by high concentrations of LPS confirms the results of our recent investigations carried out using human airways where we have demonstrated that the overnight treatment of human isolated bronchi with LPS administered at 100 ng/ml significantly inhibited the contractile tone in response to EFS [20].…”

“…The day after these treatments, equine bronchial rings were mounted into the isolated organ bath system and connected to the isometric force transducers for recording the contractile response of airway smooth muscle (ASM) in response to EFS as previously described [20].…”

“…The rings were then washed three times and allowed to stabilize. 5V, 10s, 0.5ms, biphasic pulse), as described elsewhere [18][19][20][21][22]. The contractile responses of equine bronchi evoked by EFS are mediated through vagal nerve stimulation [23], as it is tetrodotoxin sensitive [24,25].…”

Combining long‐acting bronchodilators with different mechanisms of action: A pharmacological approach to optimize bronchodilation of equine airways

“…Several neurotransmitters are released by transmural stimulation, the most representative is acetylcholine released by myelinated fibers, whereas nonmyelinated fibers mainly sustain neurogenic airway inflammation (Belvisi, ; Calzetta, Luongo, et al., ; Yu, Wang, & Robinson, ). Higher vagal frequencies activate primarily large myelinated A‐fibers, medium vagal frequencies stimulate small myelinated B‐fibers, and lower vagal frequencies induce the activation of nonmyelinated C‐fibres (Calzetta, Cazzola, et al., ; Calzetta, Luongo, et al., ; Calzetta, Rogliani, Cavalli, et al., ; Calzetta, Rogliani, Facciolo, et al., ; Calzetta, Rogliani, Mattei et al., ; Cazzola, Calzetta, Facciolo, Rogliani, & Matera, ). Therefore in this study we have stimulated equine airways by using different EFS frequencies.…”

“…However, a recent research provides the suggestion for an alternative interpretation of the cause leading to EFS hyporesponsiveness. In fact, it has been demonstrated that overnight incubation of bronchial tissue with lipopolysaccharide (LPS) may lead to desensitization of isolated airways, leading to a significant hyporesponsiveness to transmural stimulation (Cazzola et al., ). As LPS has a relevant role in the development and progression of severe equine asthma (Beeler‐Marfisi et al., ; Nevalainen et al., ; Pirie, Collie, Dixon, & McGorum, ; Pirie, Dixon, Collie, & McGorum, ; Simonen‐Jokinen, Pirie, McGorum, & Maisi, ), we cannot exclude that the bronchi used by LeBlanc et al.…”