Increased expression of p21^waf cyclin-dependent kinase inhibitor in asthmatic bronchial epithelium

Puddicombe, Sarah M., Torres-Lozano, Carlos, Richter, Audrey, Bucchieri, Fabio, Lordan, James L., Howarth, Peter H., Vrugt, Bart, Albers, Rene, Djukanovic, Ratko, Holgate, Stephen T., Wilson, Susan J. and Davies, Donna E. (2003) Increased expression of p21^waf cyclin-dependent kinase inhibitor in asthmatic bronchial epithelium. American Journal of Respiratory Cell and Molecular Biology, 28 (1), 61-68. (doi:10.1165/rcmb.4715).

Abstract

Because the asthmatic bronchial epithelium is characterized by widespread damage, we postulated that this is associated with expression of cell cycle inhibitors that control proliferation. Using bronchial biopsies, the epithelium was the major site of expression of the cyclin-dependent kinase inhibitor, p21waf. Immunostaining usually occurred in the cytoplasm of columnar cells; however, in severe asthma, nuclear staining was also evident in the proliferative, basal cell compartment. p21waf expression was significantly higher in asthmatic versus nonasthmatic epithelium and was unaffected by corticosteroid treatment; proliferating cell nuclear antigen was not significantly different in any group. p21waf, but not p27kip1, mRNA and protein were induced by treatment of bronchial epithelial cells in vitro with transforming growth factor (TGF)-ß or H2O2, but not by dexamethasone, which induced p57kip2. TGF-ß and dexamethasone inhibited epidermal growth factor (EGF)-induced DNA synthesis, whereas low concentrations of H2O2 synergized with EGF; at higher doses, growth inhibition and induction of apoptosis occurred. TGF-ß caused p21waf to become nuclear, suggesting interaction with the replicative machinery; however, in oxidant-stressed cells, p21waf was predominantly cytoplasmic, where it has been linked to cell survival. We conclude that p21waf overexpression in asthma influences cell proliferation and survival. This may cause abnormal repair responses that contribute to airway inflammation and remodeling.

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Contributors

Author: Ratko Djukanovic

Author: Susan J. Wilson

Author: Donna E. Davies

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