Tumor necrosis factor alpha (TNF alpha)-induced ICAM-1 surface expression in airway epithelial cells in vitro: possible signal transduction mechanisms
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T M Krunkosky1, B M Fischer, N J Akley
1Department of Anatomy, Physiological Sciences, and Radiology, College of Veterinary Medicine, North Carolina State University, Raleigh 27606, USA.
Insights
Tumor necrosis factor-alpha (TNF alpha) significantly increases intercellular adhesion molecule-1 (ICAM-1) on airway epithelial cells. This response is receptor-mediated via TNF-R1, involving protein kinase C and reactive oxygen species.
Area of Science:
- Pulmonary Medicine
- Immunology
- Cell Biology
Background:
- Cytokines and adhesion molecules play key roles in airway diseases like asthma.
- Tumor necrosis factor-alpha (TNF alpha) and intercellular adhesion molecule-1 (ICAM-1) are critical mediators in airway disease pathogenesis.
Purpose of the Study:
- To investigate the effects of TNF alpha on ICAM-1 surface expression in human bronchial epithelial cells.
- To elucidate the specific mechanisms underlying TNF alpha-induced ICAM-1 expression.
Main Methods:
- Primary cultures of normal human bronchial epithelial (NHBE) cells and the BEAS-2B cell line were used.
- Cells were treated with varying concentrations of TNF alpha, and ICAM-1 expression was measured by flow cytometry.
- Experiments involved heat inactivation, soluble TNF receptor (TNF-R1), a PKC inhibitor (Calphostin C), and reactive oxygen species (ROS) scavengers.
Main Results:
- TNF alpha significantly enhanced ICAM-1 surface expression in a dose- and time-dependent manner, peaking at 24 hours.
- The response was specific, as heat inactivation of TNF alpha negated the effect.
- Inhibition was observed with soluble TNF-R1 and a PKC inhibitor, while ROS scavengers enhanced TNF alpha-induced ICAM-1 expression.
Conclusions:
- TNF alpha-induced ICAM-1 expression on airway epithelium is a specific, receptor-mediated event (TNF-R1).
- The signaling pathway involves protein kinase C (PKC) and intracellular reactive oxygen species (ROS).
- Understanding these mechanisms is crucial for developing therapeutic strategies for airway inflammatory diseases.
Abstract:
Within the past several years research on the interaction of cytokines and adhesion molecules with airway epithelium in diseases has allowed us to develop a better understanding of the disease process. The cytokine, TNF alpha and the adhesion molecule ICAM-1 are important mediators in the pathogenesis of airway diseases such as asthma, chronic bronchitis, and adult respiratory distress syndrome. Effects of TNF alpha on ICAM-1 surface expression was investigated in both primary cultures of normal human bronchial epithelial (NHBE) cells and immortalized human bronchial epithelial cell line BEAS-2B. TNF alpha (0.015-150 ng/mL) significantly enhanced ICAM-1 surface expression (measured by flow cytometry) in a dose and time-dependent manner, with peak expression seen at 24 hours. This response was negated by heat inactivation of the TNF alpha prior to incubation. TNF alpha-induced ICAM-1 expression also was inhibited by pre- and coincubation of TNF alpha with 3 micrograms/mL soluble TNF-R1 or by the PKC inhibitor, Calphostin C (0.1 and 0.5 microM). The ROI scavengers, dimethylthiourea (4 mM), and dimethyl sulfoxide (0.001%), enhanced TNF alpha-induced ICAM-1 expression. Collectively, these results indicate that TNF alpha-induced ICAM-1 surface expression is a specific receptor-mediated response (TNF-R1), which is mediated by mechanisms dependent on PKC and intracellular reactive oxygen species.