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Inducible Expression of Tumor Necrosis Factor- in Transgenic Mouse Lung^*

^* From the Section of Pulmonary Disease and Critical Care Medicine, Tulane University, New Orleans, LA.

Correspondence to: Gary W. Hoyle, PhD, Associate Professor of Medicine, Section of Pulmonary Diseases and Critical Care Medicine SL9, 1430 Tulane Ave, New Orleans, LA 70112-2699

Tumor necrosis factor (TNF)- has been implicated as a key mediator of fibrotic lung disease, but the mechanisms by which it promotes fibrosis are not understood. To develop a model in which mechanisms of TNF-–induced fibrosis can be investigated in vivo, we have generated transgenic mice in which TNF- is expressed in the lung under the control of a doxycycline-inducible promoter. DNA constructs containing a mouse TNF- complementary DNA downstream from tetracycline operator and minimal cytomegalovirus promoter sequences (tetracycline-responsive element-TNF) and the reverse tetracycline transactivator downstream from the human surfactant protein-C promoter were made. Thirteen founder transgenic mice carrying both constructs were generated by coinjection of the (tetracycline-responsive element-TNF and reverse tetracycline transactivator downstream from the human surfactant protein-C promoter fragments. Offspring from founder transgenic mice were screened for inducible TNF- expression by administering doxycycline at 0.5 mg/mL in the drinking water for 7 to 10 days and collecting lung tissue for Northern blot and histologic analyses. Five of 11 lines examined thus far by Northern blot analysis exhibited TNF- transgene expression in the lung that was inducible after treatment with doxycycline. In most of the transgene-expressing lines, upregulation of the endogenous TNF- message could also be detected. This result suggested that the TNF- transgene message is translated into a biologically active polypeptide that activates expression of the endogenous TNF- gene. Histologic analysis revealed that one transgenic line exhibited prominent inflammation after induction but greatly reduced inflammation in the uninduced state. Doxycycline-treated mice had perivascular, subpleural, and alveolar inflammation that was largely confined to lymphatic spaces. The cells in the inflammatory infiltrate appeared to be primarily lymphocytes and were prominent throughout the lung. In contrast, lungs from transgenic mice not treated with doxycycline exhibited focal inflammation and had large areas with a normal appearance. These results indicate that acute upregulation of TNF- in the lung promotes a lymphocytic inflammatory response. Future experiments will determine whether long-term induction of TNF- expression results in pulmonary fibrosis.

Footnotes

Abbreviation: TNF = tumor necrosis factor

This Article Full Text (PDF) Free Submit a response Alert me when this article is cited Alert me when eLetters are posted Alert me if a correction is posted Services Email this article to a friend Similar articles in this journal Alert me to new issues of the journal Add to My Personal Article Archive Download to citation manager Citing Articles Citing Articles via Google Scholar Google Scholar Articles by Vuillemenot, B. R. Articles by Hoyle, G. W. Search for Related Content PubMed Articles by Vuillemenot, B. R. Articles by Hoyle, G. W.