Polysaccharides of Dendrobium officinale inhibit TNF-α-induced apoptosis in A-253 cell line

Our previous study demonstrated that polysaccharides of Dendrobium officinale Kimura et Migo (DP) were capable of enhancing immunomodulation in an experimental model of Sjogren's syndrome, a chronic autoimmune disease mainly affecting the salivary glands. In the present study, we further investigated the protective effect of DP on a human salivary gland cell line A-253 against tumor necrosis factor (TNF)-alpha-induced apoptosis. TNF-alpha (100 U/ml) was used as the stimulus for treating the A-253 cells to induce cellular apoptosis. Nuclear factor-kappa B (NF-kappa B, p65), phosphorylation of mitogen-activated protein kinases (MAPK), reactive oxygen species (ROS) generation, mitochondrial membrane potential and proapoptotic proteins were examined. A-253 cells were pre-treated with DP for 12 h before TNF-alpha stimulation. We observed translocation of NF-kappa B into the nuclei, prolonged MAPK, excessive ROS generation and strongly decreased mitochondrial membrane potential, and subsequently cytochrome C release and caspase-3 activation. However, pre-treatment with DP significantly inhibited the TNF-alpha-induced apoptotic factors. Our data suggested the inhibitory effect of DP on TNF-alpha-induced apoptosis in a human salivary gland cell line. This inhibition indicated potential inference of DP in the initial plasma membrane-bound complex of TNF-alpha and its receptors.