Inhibitory Effects of Anti‐Oxidants on Apoptosis of a Human Polyclonal T‐Cell Line, MT‐2, Induced by an Asbestos, Chrysotile‐A

To clarify the effects of silica and silicates on cellular features of lymphocytes, a human T‐lymphotropic virus type‐1‐immortalized polyclonal T‐cell line, MT‐2, was exposed to various concentrations of chrysotile‐A, an asbestos classified as silicate. MT‐2 cells underwent apoptosis in a dose‐ and time‐dependent manner. The mitochondrial apoptotic pathway was activated during chrysotile‐A‐induced apoptosis of MT‐2 cells, because of the phosphorylation of JNK and p38, increase of BAX and release of cytochrome‐c from mitochondria to cytoplasma. In addition, anti‐oxidants such as hydroxyl‐radical excluders and capturers of superoxide and inhibitors of superoxide production effectively reduced the size of the apoptotic fraction in MT‐2 cells cultured with chrysotile‐A. These results indicate that the activation of reactive oxygen species may play a central role in asbestos‐induced T‐cell apoptosis, and anti‐oxidants may help to prevent complications of pneumoconiosis.