Antonino Di Stefano*, Mauro Maniscalco, Bruno Balbi and Fabio L.M. Ricciardolo Pages 7149 - 7158 ( 10 )
The imbalance between increased oxidative agents and antioxidant defence mechanisms is central in the pathogenesis of obstructive lung diseases such as asthma and COPD. In these patients, there are increased levels of reactive oxygen species. Superoxide anions (O<sub>2</sub> -), Hydrogen Peroxide (H<sub>2</sub>O<sub>2</sub>) and hydroxyl radicals (•OH) are critical for the formation of further cytotoxic radicals in the bronchi and lung parenchyma. Chronic inflammation, partly induced by oxidative stress, can further increase the oxidant burden through activated phagocytic cells (neutrophils, eosinophils, macrophages), particularly in severer disease states. Antioxidants and anti-inflammatory genes are, in fact, frequently downregulated in diseased patients. Nrf2, which activates the Antioxidant Response Element (ARE) leading to upregulation of GPx, thiol metabolism-associated detoxifying enzymes (GSTs) and stressresponse genes (HO-1) are all downregulated in animal models and patients with asthma and COPD. An exaggerated production of Nitric Oxide (NO) in the presence of oxidative stress can promote the formation of oxidizing reactive nitrogen species, such as peroxynitrite (ONO<sub>2</sub> -), leading to nitration and DNA damage, inhibition of mitochondrial respiration, protein dysfunction, and cell damage in the biological systems. Protein nitration also occurs by activation of myeloperoxidase and H<sub>2</sub>O<sub>2</sub>, promoting oxidation of nitrite (NO<sub>2</sub> -). There is increased nitrotyrosine and myeloperoxidase in the bronchi of COPD patients, particularly in severe disease. The decreased peroxynitrite inhibitory activity found in induced sputum of COPD patients correlates with pulmonary function. Markers of protein nitration - 3- nitrotyrosine, 3-bromotyrosine, and 3-chlorotyrosine - are increased in the bronchoalveolar lavage of severe asthmatics. Targeting the oxidative, nitrosative stress and associated lung inflammation through the use of either denitration mechanisms or new drug delivery strategies for antioxidant administration could improve the treatment of these chronic disabling obstructive lung diseases.
Oxidative stress, asthma, COPD, inflammation, nitrosative stress, pathogenesis.
Divisione di Pneumologia e Laboratorio di Immunopatologia dell’Apparato Cardio Respiratorio, Istituti Clinici Scientifici Maugeri SpA, Societa Benefit, IRCCS, Veruno, Divisione di Pneumologia, Istituti Clinici Scientifici Maugeri SpA, Societa Benefit, IRCCS, Telese, Divisione di Pneumologia e Laboratorio di Immunopatologia dell’Apparato Cardio Respiratorio, Istituti Clinici Scientifici Maugeri SpA, Societa Benefit, IRCCS, Veruno, Dipartimento di Scienze Cliniche e Biologiche, AOU, San Luigi, Orbassano, Universita di Torino, Torino