TXL-mediated protection against PA-induced endothelial apoptosis. PA at the concentration of 0.5 mM was used to treat endothelial cells with or without TXL preconditioning. TXL preconditioning was carried out by adding ethanol extracted TXL (100 μg/ml) to cultured endothelial cells 30 min prior to the exposure of PA. Apoptosis was detected using TUNEL assay in which DAPI stained nuclei blue. Percentages of apoptosis were calculated as the number of nuclei with positive TUNEL stain to the total number of nuclei (DAPI stain). Cells were visualized under fluorescence microscope (magnification × 200).