Bleomycin induces caveolin-1 and -2 expression in epithelial lung cancer A549 cells

Abstract

Background: Bleomycin induces apoptosis in alveolar epithelial cells. The expression of caveolin-1 and -2 in lung epithelial-derived A549 cells was analysed in terms of apoptosis after exposure to bleomycin.

Materials and methods: Apoptosis was investigated using flow cytometry, ELISA, immunohistochemistry and Western blot analysis. Caveolin-1 and -2 were determined at the protein level (Western blot). Intracellular caveolin-1 distribution was studied with immunofluorescence, as well as sucrose density gradient centrifugation.

Results: Caveolin-1 and -2 were up-regulated 1 h after exposure to bleomycin and preceding the occurrence of caspase-8, and of caspase-3 and caspase-9 cleavage products. Sucrose density gradient centrifugation revealed that bleomycin exposure led to a partial translocation of caveolin-1 from caveolin-rich membrane fractions to non-raft fractions. Successful inhibition of bleomycin-induced apoptosis by the broad-spectrum caspase inhibitor zVAD-fmk did not influence the amount of caveolin-1 and -2.

Conclusion: The early up-regulation of caveolin-1 and -2 following bleomycin exposure is a rather apoptosis-independent event related to other unknown mechanisms of bleomycin-mediated cell injury.