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Tumor necrosis factor-alpha-induced lung cell expression of antiapoptotic genes TRAF1 and cIAP2
G S Pryhuber1, H L Huyck, R J Staversky
1Department of Pediatrics and Environmental Medicine, University of Rochester Medical Center, Rochester, New York 14642, USA. pryh@uhura.cc.rochester.edu
Abstract:
Tumor necrosis factor (TNF) receptor (TNFR)-associated factors 1 and 2 (TRAF1 and TRAF2) and inhibitor of apoptosis proteins cIAP1 (MIHB) and cIAP2 (MIHC) were recently identified as proteins that associate with the TNF-alpha receptors TNFRI (p55) and TNFRII (p75) and inhibit TNF-alpha-induced programmed cell death or apoptosis. In the original reports, TRAF1 expression, unlike the ubiquitous TRAF2, was restricted to specific tissues in the lung, spleen, and testis. TNF-alpha is increased in the lung in many forms of pulmonary disease. In the current study, Western analysis, immunohistochemistry, and ribonuclease protection assays were used to determine whether TNF-alpha regulates the expression of these TNFR-associated proteins in lung cells. We demonstrate for the first time TNF-alpha dose-dependent induction of TRAF1 protein and messenger RNA (mRNA) in human H441 and A549 pulmonary adenocarcinoma cell lines, as well as in lung cells of C57BL/6J mice after intratracheal administration of TNF-alpha. In contrast to the epithelial cells, TRAF1 was not induced by TNF-alpha in U937 cells, a human monocytic cell line, suggesting cell type-specific regulation. Similarly, cIAP2 mRNA was induced by TNF-alpha in both H441 and A549 pulmonary epithelial cells but not in U937 cells. TNF-alpha is a primary mediator of acute pulmonary inflammation and contributes to the pathophysiology of chronic lung diseases such as bronchopulmonary dysplasia (BPD), a fibrotic disease of prematurely born infants. Immunohistochemical staining of human neonatal lung tissue demonstrated increased TRAF1 in lungs of infants dying of pneumonia or BPD in comparison with those dying of congenital malformation. These studies support the hypothesis that the TRAF1 and cIAP2 genes are highly regulated in pulmonary cells and may play a role in human lung disease.
Insights
Tumor necrosis factor-alpha (TNF-alpha) induces tumor necrosis factor receptor-associated factor 1 (TRAF1) and cIAP2 in lung cells, suggesting their role in pulmonary diseases like bronchopulmonary dysplasia.
Area of Science:
- Molecular Biology
- Immunology
- Pulmonary Medicine
Background:
- Tumor necrosis factor receptor (TNFR)-associated factors (TRAFs) and inhibitor of apoptosis proteins (cIAPs) are critical in TNF-alpha signaling.
- TRAF1 expression is typically restricted to specific tissues, unlike TRAF2.
- Elevated TNF-alpha in the lung is linked to various pulmonary diseases.
Purpose of the Study:
- To investigate whether TNF-alpha regulates TRAF1 and cIAP2 expression in lung cells.
- To determine the cell type-specific regulation of these proteins by TNF-alpha.
- To explore the potential role of TRAF1 and cIAP2 in human lung diseases.
Main Methods:
- Western analysis and ribonuclease protection assays to detect protein and mRNA levels.
- Immunohistochemistry to visualize protein expression in lung tissues.
- Intratracheal administration of TNF-alpha in mouse models and cell line studies.
Main Results:
- TNF-alpha dose-dependently induced TRAF1 protein and mRNA in human pulmonary adenocarcinoma cell lines (H441, A549) and mouse lung cells.
- TRAF1 induction by TNF-alpha was cell type-specific, occurring in epithelial cells but not in U937 monocytic cells.
- TNF-alpha also induced cIAP2 mRNA in H441 and A549 cells, but not in U937 cells.
- Increased TRAF1 expression was observed in the lungs of infants with pneumonia or bronchopulmonary dysplasia (BPD).
Conclusions:
- TRAF1 and cIAP2 gene expression is highly regulated in pulmonary cells by TNF-alpha.
- These findings support a potential role for TRAF1 and cIAP2 in the pathophysiology of human lung diseases, including BPD.