We have investigated the role of the cytoskeleton in surfactant protein gene expression. Cytochalasin D (CD), colchicine (Col), or nocodazole (Noco) were tested on primary cultures of adult rat alveolar type II cells. Treatment with any of the drugs did not result in dramatic cell shape changes, but ultrastructural examination revealed that the cytoplasm of cells treated with CD was markedly disorganized; cells treated with Col did not exhibit such changes. Treatment with any of the three drugs resulted in a reduction in surfactant protein (SP) mRNAs. These decreases were not the result of cell toxicity, since overall protein synthesis was unimpaired by drug treatment. Washing the cells followed by an additional 2 days of culture resulted in a reaccumulation of SP mRNAs in CD-treated cells but not in Col-treated cells. Washing of Noco-treated cultures resulted in partial recovery. SP mRNA stability was estimated in the presence or absence of cytoskeleton-disrupting drugs. Disruption of either microfilaments or microtubules significantly affected the half-lives of mRNAs for SP-A, SP-B, and SP-C. These data support a role for the cytoskeleton in the maintenance of type II cell differentiation and suggest that the role of the cytoskeleton is at least in part to stabilize SP mRNAs.
Effects of bone marrow-derived mesenchymal stromal cells on gene expression in human alveolar type II cells exposed to TNF-α
, IL-1β
, and IFN-γ
