Production of tumour necrosis factor alpha by primary cultured rat alveolar epithelial cells

Tumour necrosis factor alpha(TNF-alpha) is one of the most important pro-in flammatory cytokines, which plays an important role in host defense and acu te inflammation related to tissue injury. The major source of TNF-alpha has been shown to be immune cells such as macrophages and neutrophils, In the present study, we demonstrated that LPS-treatment on alveolar epithelial ce lls isolated from adult rat lungs also induced a dose- and time-dependent r elease of TNF-alpha, The purity and identity of these cells were examined b y immunofluorescent staining and confocal microscopy with antibodies for cy tokeratin and pro-surfactant protein C, markers for epithelial cells and ty pe II pneumocytes respectively. Positive staining of TNF-alpha was observed throughout the cell layer and localized intracellularly, LPS-induced TNF-a lpha production from alveolar epithelial cells was blocked not only by cycl oheximide, an inhibitor of protein translation, but also by actinomycin D, an inhibitor of gene transcription. The mRNA of TNF-alpha rapidly increased within 1 h of LPS stimulation. These data suggest that LPS-induced TNF-alp ha production from alveolar epithelial cells is primarily regulated at the transcriptional level, which is different from that of macrophages and neut rophils, TNF-alpha produced by alveolar epithelial cells may function as an alert signal in host defense to induce production of other inflammatory me diators. (C) 2000 Academic Press.