Fig. 1.

Cigarette smoke is a complex mixture of thousands of chemical compounds including free radicles and oxidants. Cigarette smoke activates alveolar and bronchial epithelial cells (1) to elicit inflammatory responses leading to the release of cytokines and recruitment of neutrophils. Endogenous oxidants (2) and proteases (3) are generated from neutrophils and other phagocytic cells (macrophages) (4) increasing the oxidative burden in the lung. The lung has an efficient antioxidant (5) and anti-protease systems (6). The balance between the oxidants and the anti- oxidants is deranged by the exogenously and endogenously produced oxidants by the cigarette smoke leading to oxidative stress (7). Oxidative stress also contributes to mucus hypersecretion (8), apoptosis (9) and inflammation (10).