The role of oxidative stress in the biological responses of lung epithelial cells to cigarette smoke.

The mechanism(s) by which cigarette smoke contributes to lung diseases, such as cancer, remains unclear. Recent developments in our knowledge of cell signalling events suggest that cigarette smoke causes oxidative stress and proinflammatory responses in cells of the lung. Cigarette smoke is a complex mixture of over 4000 compounds and high levels of oxidants and reactive oxygen species (ROS) have been detected in both mainstream and sidestream smoke. Oxidative stress that ensues, when the antioxidant defences are depleted, is accompanied by increases in ROS production in lung epithelial cells. Cigarette smoke-mediated oxidative stress produces DNA damage and activates survival signalling cascades resulting in uncontrolled cell proliferation and transformation. Intervention studies using antioxidants have provided compelling evidence that oxidative stress plays a critical role in the aetiology of smoking-related disorders.