Induction of type Ⅱ alveolar epithelial cells apoptosis in mouse by lipopolysaccharide does not require TNF-α

To examine whether lipopolysaccharide (LPS)-induced apoptosis correlates with TNF-α release by type Ⅱ alveolar epithelial cells (AEC Ⅱ), whether TNF-α knockout (TNF KO) abrogates the induction of apoptosis by LPS and whether TNF-α is sufficient to induce apoptosis in this cell type Methods AEC Ⅱ were isolated from wild type mice and TNF KO mice Cells were stimulated with LPS or recombinant murine TNF-α for 24 h TNF-α in culture supernatant was determined by ELISA following LPS stimulation Apoptosis was determined by the terminal deoxynucleotidyl transferase end-labeling (TUNEL) assay after treatment with either LPS or TNF-α Results LPS induced apoptosis in wild type AEC Ⅱ in a concentration-dependent manner LPS-induced AEC Ⅱ apoptosis was accompanied by an 11-fold increase (from 0 073±0 065 ng/ml in control to 0 94±0 14 ng/ml in 50 μg/ml of LPS, P<0 01) in TNF-α release However, increasing concentrations (5 or 25 ng/ml) of recombinant murine TNF-α failed to induce AEC Ⅱ apoptosis In addition, apoptosis did occur in AEC Ⅱ isolated from TNF KO mice following LPS stimulation Conclusions This study confirms that LPS induces TNF-α release and apoptosis in murine AEC Ⅱ in vitro Exogenous TNF-α failed to induce AEC Ⅱ apoptosis, and apoptosis occurred following LPS stimulation in cells lacking the ability to produce TNF-α Taken together, these results suggest that LPS-induced AEC Ⅱ apoptosis occurs by a TNF-α-independent mechanism