Abstract: Objective To investigate whether the nucleotide-binding oligomerization-2(NOD2)-mideated tolerance phenomenon exists in microglia cells and its relationship with Caspase-1 activity. Methods After microglia cells were stimulated with different concentrations of MDP or S.pneumonia for 24 h, the expressions of NOD2 and NF-κB were detected by Western blotting and the expressions of IL-6 and TNF-α were detected by ELISA. After microglia cells were pre-treated with MDP (100 μg/mL) for 0, 3 or 24 h, the expressions of IL-6 and TNF-α were detected by ELISA to verify the NOD2-mediated tolerance in microglia. After Caspase-1 activity was activated or suppressed by ATP or Caspase-1 inhibitor, the expressions of IL-6 and TNF-α were detected by ELISA to observe the relationship between NOD2-mediated tolerance and Caspase-1. Results Compared with no treatment, MDP and S.pneumonia treatment for 24 h significantly increased the levels of NOD2, NF-κB, IL-6 and TNF-α in microglia cells(P<0.05). MDP pretreatment for 3 or 24 h reduced secretion of IL-6 and TNF-α upon subsequent stimulation of MDP for 24 h. Levels of IL-6 and TNF-α were significantly down-regulated by ATP pretreatment, while up-regulated by Caspase-1 inhibitor treatment.Conclusion Prolonged periods of MDP exposure can induce NOD2-mediated tolerance in microglia cells and NOD2-mediated tolerance is associated with Caspase-1 activity.

Key words: Tolerance, ATP, Nucleotide-binding oligomerization-2, Microglia, Caspase-1