Role of cyclins in epithelial response to oxidants.

Oxidants are involved in a large variety of pulmonary diseases. Among the various cell types that compose the respiratory system, the epithelial cells appear to be a major target for oxidative stress. When cells are exposed to DNA-damaging agents such as oxidants, a feedback control is activated that acts as a brake on the cell cycle to inhibit entry into the S phase until DNA repair is completed. Progression through the G1 phase and the G1-S transition involves sequential assembly and activation of key regulators of the cell cycle machinery, the cyclin-dependent kinases (CDKs). Activity of the CDKs is regulated by several mechanisms, which include the CDK inhibitors (CKIs). The CKI p21(CIP1) appears to play an important role in the response of epithelial cells to oxidants.