CAV1 and pulmonary emphysema: Basedon our findings, we propose caveolin-1 as a novel upstream positive regulatorof p53 in the signaling pathway that leads to premature senescence of lungfibroblasts upon oxidant stimulation and, eventually, to pulmonary emphysema.We currently do not know whether cigarette smoke induces premature senescenceof other lung cell types, such as alveolar epithelial cells, which mediateoxygen absorption.