The stress response and the lung

The stress response is a highly conserved cellular defense mechanism defined by the rapid and specific expression of stress proteins, with concomitant transient inhibition of nonstress protein gene expression. The stress proteins mediate cellular and tissue protection against diverse cytotoxic stimuli. Among the many classes of stress proteins, heat shock protein 70 and heme oxygenase-1 are the best characterized with respect to lung biology. A potential role for stress proteins in human lung disease is inferred from studies demonstrating stress protein expression in the lungs of patients with cancer, asthma, and acute lung injury. Several examples of stress protein-mediated cytoprotection exist in cell and animal models of acute lung injury. Stress protein induction protects rats against acute lung injury caused by either systemic administration of endotoxin or intratracheal administration of phospholipase A(1). In vitro, increased expression of stress proteins protects lung cells against endotoxin-mediated apoptosis and oxidant injury. The mechanisms of stress response-mediated cytoprotection may involve the enzymatic and molecular chaperone properties of stress proteins. Alternatively, the stress response may protect by modulating lung proinflammatory responses. Data from extrapulmonary systems suggest that stress response-associated factors (heat shock protein 70 and heat shock factor) are directly involved in modulation of proinflammatory gene expression. Recent evidence also demonstrates interactions between the stress response and the I-kappa B/nuclear factor-kappa B pathway in cultured lung cells. Increased understanding about the role of stress proteins in lung biology may support efforts to selectively increase expression of one or more stress proteins to provide protection against human acute lung injury.